diff --git a/Dockerfile b/Dockerfile
index 1c2324dd1..098a7630f 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -58,7 +58,7 @@ COPY server/requirements/kobo-cloudscraper.txt /tmp/kobo-cloudscraper-requiremen
 # pip is build-only here. Leaving it installed also leaves pip/_vendor/vendor.txt,
 # which Trivy reads as installed msgpack and setuptools and fails the image scan on.
 RUN apk upgrade --no-cache && \
-    apk add --no-cache poppler-utils su-exec ffmpeg python3 py3-pip tini && \
+    apk add --no-cache poppler-utils su-exec ffmpeg python3 py3-pip tini tzdata && \
     python3 -m venv /opt/bookorbit-python && \
     /opt/bookorbit-python/bin/python -m pip install --no-cache-dir -r /tmp/kobo-cloudscraper-requirements.txt && \
     /opt/bookorbit-python/bin/python -m pip uninstall -y pip && \
diff --git a/docker-compose.yml b/docker-compose.yml
index 8892f9472..b0eca0b91 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -23,6 +23,7 @@ services:
       SETUP_BOOTSTRAP_TOKEN: ${SETUP_BOOTSTRAP_TOKEN?required}
       APP_URL: ${APP_URL?required}
       CLIENT_URL: ${CLIENT_URL:-${APP_URL?required}}
+      TZ: ${TZ:-UTC}
       PUID: ${PUID:-1000}
       PGID: ${PGID:-1000}
       NODE_MAX_OLD_SPACE_SIZE: ${NODE_MAX_OLD_SPACE_SIZE:-auto}
diff --git a/server/src/common/utils/timezone.utils.test.ts b/server/src/common/utils/timezone.utils.test.ts
index cf00819e5..4cd529f45 100644
--- a/server/src/common/utils/timezone.utils.test.ts
+++ b/server/src/common/utils/timezone.utils.test.ts
@@ -1,6 +1,6 @@
 import { describe, expect, it } from 'vitest';
 
-import { isDateKey, isValidTimeZone, resolveTimeZone, toDateKeyInTimeZone, toTimeZoneStartOfDay } from './timezone.utils';
+import { getYearInTimeZone, isDateKey, isValidTimeZone, resolveTimeZone, toDateKeyInTimeZone, toTimeZoneStartOfDay } from './timezone.utils';
 
 describe('timezone utils', () => {
   it('validates IANA timezones and rejects invalid values', () => {
@@ -66,4 +66,11 @@ describe('timezone utils', () => {
   it('throws when date key is malformed', () => {
     expect(() => toTimeZoneStartOfDay('2026-02-30', 'UTC')).toThrow(RangeError);
   });
+
+  it("reads the year in the given timezone, not the host's", () => {
+    const newYearsEveUtc = new Date('2026-12-31T23:30:00.000Z');
+    expect(getYearInTimeZone(newYearsEveUtc, 'UTC')).toBe(2026);
+    expect(getYearInTimeZone(newYearsEveUtc, 'Pacific/Auckland')).toBe(2027);
+    expect(getYearInTimeZone(newYearsEveUtc, 'America/New_York')).toBe(2026);
+  });
 });
diff --git a/server/src/common/utils/timezone.utils.ts b/server/src/common/utils/timezone.utils.ts
index c702afb68..c2a6e7473 100644
--- a/server/src/common/utils/timezone.utils.ts
+++ b/server/src/common/utils/timezone.utils.ts
@@ -104,3 +104,7 @@ export function toTimeZoneStartOfDay(dateKey: string, timeZone: string): Date {
 
   throw new RangeError(`Invalid timezone conversion for date key: ${dateKey}`);
 }
+
+export function getYearInTimeZone(date: Date, timeZone: string): number {
+  return Number(toDateKeyInTimeZone(date, timeZone).slice(0, 4));
+}
diff --git a/server/src/modules/achievement/achievement.repository.test.ts b/server/src/modules/achievement/achievement.repository.test.ts
index 2b2e1f915..91b6302a7 100644
--- a/server/src/modules/achievement/achievement.repository.test.ts
+++ b/server/src/modules/achievement/achievement.repository.test.ts
@@ -10,6 +10,19 @@ function flattenSql(value: unknown): string {
   return [flattenSql(record.value), flattenSql(record.queryChunks)].join(' ');
 }
 
+/** Collects the primitives drizzle binds into a query, so tests can assert on parameters rather than SQL text. */
+function boundValues(node: unknown, out: unknown[] = [], seen = new Set<unknown>()): unknown[] {
+  if (node === null || node === undefined || seen.has(node)) return out;
+  if (typeof node === 'string' || typeof node === 'number' || node instanceof Date) {
+    out.push(node instanceof Date ? node.toISOString() : node);
+    return out;
+  }
+  if (typeof node !== 'object') return out;
+  seen.add(node);
+  for (const value of Object.values(node as Record<string, unknown>)) boundValues(value, out, seen);
+  return out;
+}
+
 function makeSelectChain(resolvedValue: unknown) {
   const chain: Record<string, ReturnType<typeof vi.fn>> = {};
   const methods = ['from', 'where', 'orderBy', 'limit', 'groupBy', 'innerJoin', 'leftJoin', 'having', 'as', '$dynamic'];
@@ -618,7 +631,7 @@ describe('AchievementRepository', () => {
       const db = { execute: vi.fn().mockResolvedValue({ rows: [{ streak_length: '7' }] }) };
       const repo = makeRepo(db);
 
-      const result = await repo.getCurrentStreak(1);
+      const result = await repo.getCurrentStreak(1, 'UTC');
 
       expect(result).toBe(7);
     });
@@ -627,12 +640,88 @@ describe('AchievementRepository', () => {
       const db = { execute: vi.fn().mockResolvedValue({ rows: [] }) };
       const repo = makeRepo(db);
 
-      const result = await repo.getCurrentStreak(1);
+      const result = await repo.getCurrentStreak(1, 'UTC');
 
       expect(result).toBe(0);
     });
   });
 
+  describe('reader-timezone day bucketing', () => {
+    // user_reading_daily_stats.day and reading_sessions are bucketed in the reader's timezone,
+    // so every "in a day" query has to agree with that rather than with UTC or the database server.
+    it("getCurrentStreak cuts off at the reader's today, not the database server's CURRENT_DATE", async () => {
+      const db = { execute: vi.fn().mockResolvedValue({ rows: [{ streak_length: '4' }] }) };
+      const repo = makeRepo(db);
+      vi.useFakeTimers();
+      vi.setSystemTime(new Date('2026-08-23T22:30:00.000Z'));
+
+      await repo.getCurrentStreak(1, 'Pacific/Auckland');
+
+      const sql = flattenSql(db.execute.mock.calls[0]![0]);
+      expect(sql).not.toContain('CURRENT_DATE');
+      // 22:30 UTC on the 23rd is already the 24th in Auckland.
+      expect(boundValues(db.execute.mock.calls[0]![0])).toContain('2026-08-24');
+      vi.useRealTimers();
+    });
+
+    it("getMaxPagesInADay groups by the reader's local day", async () => {
+      const db = { execute: vi.fn().mockResolvedValue({ rows: [{ max_pages: 10 }] }) };
+      const repo = makeRepo(db);
+
+      await repo.getMaxPagesInADay(1, 'Pacific/Auckland');
+
+      expect(flattenSql(db.execute.mock.calls[0]![0])).toContain('AT TIME ZONE');
+      expect(boundValues(db.execute.mock.calls[0]![0])).toContain('Pacific/Auckland');
+    });
+
+    it("getPagesOnDay windows the day in the reader's timezone", async () => {
+      const chain = makeSelectChain([{ value: 42 }]);
+      const repo = makeRepo({ select: vi.fn().mockReturnValue(chain) });
+
+      await repo.getPagesOnDay(1, new Date('2026-08-23T22:30:00.000Z'), 'Pacific/Auckland');
+
+      const bounds = boundValues(chain.where!.mock.calls[0]![0]);
+      // Auckland is UTC+12, so their 24th runs from 12:00 UTC on the 23rd to 12:00 UTC on the 24th.
+      expect(bounds).toContain('2026-08-23T12:00:00.000Z');
+      expect(bounds).toContain('2026-08-24T12:00:00.000Z');
+    });
+
+    it("countAnnotationsOnDay windows the day in the reader's timezone", async () => {
+      const chain = makeSelectChain([{ value: 3 }]);
+      const repo = makeRepo({ select: vi.fn().mockReturnValue(chain) });
+
+      await repo.countAnnotationsOnDay(1, new Date('2026-08-23T22:30:00.000Z'), 'Pacific/Auckland');
+
+      const bounds = boundValues(chain.where!.mock.calls[0]![0]);
+      expect(bounds).toContain('2026-08-23T12:00:00.000Z');
+      expect(bounds).toContain('2026-08-24T12:00:00.000Z');
+    });
+  });
+
+  describe('findUserTimeZone', () => {
+    it("returns the reader's configured timezone", async () => {
+      const chain = makeSelectChain([{ settings: { timezone: 'Europe/Stockholm' } }]);
+      const repo = makeRepo({ select: vi.fn().mockReturnValue(chain) });
+
+      await expect(repo.findUserTimeZone(1)).resolves.toBe('Europe/Stockholm');
+    });
+
+    it('falls back to UTC for a missing or unusable timezone', async () => {
+      for (const settings of [{}, { timezone: '' }, { timezone: 'Not/AZone' }, null]) {
+        const chain = makeSelectChain([{ settings }]);
+        const repo = makeRepo({ select: vi.fn().mockReturnValue(chain) });
+        await expect(repo.findUserTimeZone(1)).resolves.toBe('UTC');
+      }
+    });
+
+    it('falls back to UTC when the user row is missing', async () => {
+      const chain = makeSelectChain([]);
+      const repo = makeRepo({ select: vi.fn().mockReturnValue(chain) });
+
+      await expect(repo.findUserTimeZone(1)).resolves.toBe('UTC');
+    });
+  });
+
   describe('countDistinctMonthsWithReading', () => {
     it('returns count of distinct months with reading', async () => {
       const chain = makeSelectChain([{ month: '1' }, { month: '3' }, { month: '7' }]);
@@ -1786,7 +1875,7 @@ describe('AchievementRepository', () => {
       const db = { execute: vi.fn().mockResolvedValue({ rows: [{ max_pages: 203.7 }] }) };
       const repo = makeRepo(db);
 
-      const result = await repo.getMaxPagesInADay(1);
+      const result = await repo.getMaxPagesInADay(1, 'UTC');
 
       expect(result).toBe(203);
     });
@@ -1795,7 +1884,7 @@ describe('AchievementRepository', () => {
       const db = { execute: vi.fn().mockResolvedValue({ rows: [{ max_pages: 0 }] }) };
       const repo = makeRepo(db);
 
-      const result = await repo.getMaxPagesInADay(1);
+      const result = await repo.getMaxPagesInADay(1, 'UTC');
 
       expect(result).toBe(0);
     });
@@ -1804,7 +1893,7 @@ describe('AchievementRepository', () => {
       const db = { execute: vi.fn().mockResolvedValue({ rows: [] }) };
       const repo = makeRepo(db);
 
-      const result = await repo.getMaxPagesInADay(1);
+      const result = await repo.getMaxPagesInADay(1, 'UTC');
 
       expect(result).toBe(0);
     });
diff --git a/server/src/modules/achievement/achievement.repository.ts b/server/src/modules/achievement/achievement.repository.ts
index e8bc65b22..34434dbe5 100644
--- a/server/src/modules/achievement/achievement.repository.ts
+++ b/server/src/modules/achievement/achievement.repository.ts
@@ -2,6 +2,8 @@ import { Inject, Injectable } from '@nestjs/common';
 import { and, count, countDistinct, desc, eq, gt, gte, isNotNull, isNull, lt, lte, ne, notInArray, sql, sum } from 'drizzle-orm';
 import { NodePgDatabase } from 'drizzle-orm/node-postgres';
 
+import { addDateKeyDays } from '../../common/utils/reading-daily-stats.utils';
+import { resolveTimeZone, toDateKeyInTimeZone, toTimeZoneStartOfDay } from '../../common/utils/timezone.utils';
 import { DB } from '../../db';
 import * as schema from '../../db/schema';
 import {
@@ -110,6 +112,11 @@ export class AchievementRepository {
     return row?.isSuperuser ?? false;
   }
 
+  async findUserTimeZone(userId: number): Promise<string> {
+    const [row] = await this.db.select({ settings: users.settings }).from(users).where(eq(users.id, userId)).limit(1);
+    return resolveTimeZone((row?.settings as { timezone?: unknown } | undefined)?.timezone, 'UTC');
+  }
+
   async countFinishedBooks(userId: number): Promise<number> {
     const [{ value }] = await this.db
       .select({ value: count() })
@@ -265,8 +272,11 @@ export class AchievementRepository {
     return row?.title ?? null;
   }
 
-  async getCurrentStreak(userId: number): Promise<number> {
-    // Count consecutive days with reading activity ending at today or yesterday
+  async getCurrentStreak(userId: number, timeZone: string): Promise<number> {
+    // Count consecutive days with reading activity ending at today or yesterday.
+    // `day` is bucketed in the reader's timezone, so the "is it still alive" cutoff
+    // has to be their today too, not the database server's CURRENT_DATE.
+    const today = toDateKeyInTimeZone(new Date(), timeZone);
     const result = await this.db.execute(sql`
       WITH daily AS (
         SELECT DISTINCT day::date as d
@@ -280,7 +290,7 @@ export class AchievementRepository {
       SELECT COUNT(*) as streak_length
       FROM streak
       WHERE grp = (
-        SELECT grp FROM streak WHERE d >= CURRENT_DATE - INTERVAL '1 day' ORDER BY d DESC LIMIT 1
+        SELECT grp FROM streak WHERE d >= ${today}::date - INTERVAL '1 day' ORDER BY d DESC LIMIT 1
       )
     `);
     const rows = (result as unknown as { rows: Array<{ streak_length: string }> }).rows;
@@ -679,9 +689,10 @@ export class AchievementRepository {
     return rows.length > 0 ? rows[0].cnt : 0;
   }
 
-  async countAnnotationsOnDay(userId: number, date: Date): Promise<number> {
-    const dayStart = new Date(Date.UTC(date.getUTCFullYear(), date.getUTCMonth(), date.getUTCDate()));
-    const dayEnd = new Date(dayStart.getTime() + 24 * 60 * 60 * 1000);
+  async countAnnotationsOnDay(userId: number, date: Date, timeZone: string): Promise<number> {
+    const day = toDateKeyInTimeZone(date, timeZone);
+    const dayStart = toTimeZoneStartOfDay(day, timeZone);
+    const dayEnd = toTimeZoneStartOfDay(addDateKeyDays(day, 1), timeZone);
     const [{ value }] = await this.db
       .select({ value: count() })
       .from(annotations)
@@ -988,9 +999,10 @@ export class AchievementRepository {
     return Math.floor(Number(result?.value ?? 0));
   }
 
-  async getPagesOnDay(userId: number, day: Date): Promise<number> {
-    const dayStart = new Date(Date.UTC(day.getUTCFullYear(), day.getUTCMonth(), day.getUTCDate()));
-    const dayEnd = new Date(dayStart.getTime() + 24 * 60 * 60 * 1000);
+  async getPagesOnDay(userId: number, day: Date, timeZone: string): Promise<number> {
+    const dayKey = toDateKeyInTimeZone(day, timeZone);
+    const dayStart = toTimeZoneStartOfDay(dayKey, timeZone);
+    const dayEnd = toTimeZoneStartOfDay(addDateKeyDays(dayKey, 1), timeZone);
     const [result] = await this.db
       .select({
         value: sql<number>`coalesce(sum(${bookMetadata.pageCount} * least(greatest(${readingSessions.progressDelta}, 0), 100) / 100.0), 0)::float`,
@@ -1014,7 +1026,7 @@ export class AchievementRepository {
     return Math.floor(Number(result?.value ?? 0));
   }
 
-  async getMaxPagesInADay(userId: number): Promise<number> {
+  async getMaxPagesInADay(userId: number, timeZone: string): Promise<number> {
     const result = await this.db.execute<{ max_pages: number }>(sql`
       SELECT COALESCE(MAX(day_pages), 0)::float AS max_pages FROM (
         SELECT SUM(bm.page_count * LEAST(GREATEST(rs.progress_delta, 0), 100) / 100.0) AS day_pages
@@ -1025,7 +1037,7 @@ export class AchievementRepository {
           AND bm.page_count IS NOT NULL AND bm.page_count > 0
           AND rs.progress_delta IS NOT NULL AND rs.progress_delta > 0 AND rs.progress_delta <= 100
           AND rs.duration_seconds > 0
-        GROUP BY DATE_TRUNC('day', rs.started_at AT TIME ZONE 'UTC')
+        GROUP BY DATE_TRUNC('day', rs.started_at AT TIME ZONE ${timeZone})
       ) daily
     `);
     const rows = (result as unknown as { rows: Array<{ max_pages: number }> }).rows;
diff --git a/server/src/modules/achievement/achievement.service.test.ts b/server/src/modules/achievement/achievement.service.test.ts
index 27ca250b2..628417bae 100644
--- a/server/src/modules/achievement/achievement.service.test.ts
+++ b/server/src/modules/achievement/achievement.service.test.ts
@@ -9,6 +9,7 @@ function makeRepo() {
     findUserAchievements: vi.fn().mockResolvedValue([]),
     findUserEarnedKeys: vi.fn().mockResolvedValue(new Set()),
     findUserIsSuperuser: vi.fn().mockResolvedValue(false),
+    findUserTimeZone: vi.fn().mockResolvedValue('UTC'),
     award: vi.fn().mockResolvedValue({ id: 1, achievementKey: 'test', userId: 1, awardedAt: new Date(), contextJson: null }),
     upsertCatalogue: vi.fn().mockResolvedValue(undefined),
     countFinishedBooks: vi.fn().mockResolvedValue(0),
diff --git a/server/src/modules/achievement/achievement.service.ts b/server/src/modules/achievement/achievement.service.ts
index 7c220feaa..59d49ce1e 100644
--- a/server/src/modules/achievement/achievement.service.ts
+++ b/server/src/modules/achievement/achievement.service.ts
@@ -2,6 +2,7 @@ import { Injectable, Logger, OnModuleDestroy, OnModuleInit } from '@nestjs/commo
 import { NotificationType, ACHIEVEMENT_CATEGORY_LABELS } from '@bookorbit/types';
 import type { AchievementCatalogueResponse, AchievementCategoryGroup, AchievementItem, AchievementCategory } from '@bookorbit/types';
 import { sanitizeLogValue } from '../../common/utils/log-sanitize.utils';
+import { getYearInTimeZone, resolveTimeZone, toDateKeyInTimeZone } from '../../common/utils/timezone.utils';
 import type { RequestUser } from '../../common/types/request-user';
 
 import { NotificationService } from '../notification/notification.service';
@@ -61,7 +62,8 @@ export class AchievementService implements OnModuleInit, OnModuleDestroy {
       earnedMap.set(ua.achievementKey, ua);
     }
 
-    const progressMap = await this.computeProgress(userId, user.isSuperuser, allAchievements, earnedMap);
+    const timeZone = resolveTimeZone((user.settings as { timezone?: unknown } | undefined)?.timezone, 'UTC');
+    const progressMap = await this.computeProgress(userId, user.isSuperuser, timeZone, allAchievements, earnedMap);
 
     const categoryOrder: AchievementCategory[] = ['reading', 'library', 'exploration', 'dedication', 'devices'];
     const grouped = new Map<AchievementCategory, AchievementItem[]>();
@@ -127,8 +129,12 @@ export class AchievementService implements OnModuleInit, OnModuleDestroy {
     try {
       if (!(await this.userService.isAchievementEnabled(userId))) return;
 
-      const [earnedKeys, isSuperuser] = await Promise.all([this.repo.findUserEarnedKeys(userId), this.repo.findUserIsSuperuser(userId)]);
-      const awards = await this.registry.evaluate({ userId, isSuperuser, eventName, payload }, earnedKeys);
+      const [earnedKeys, isSuperuser, timeZone] = await Promise.all([
+        this.repo.findUserEarnedKeys(userId),
+        this.repo.findUserIsSuperuser(userId),
+        this.repo.findUserTimeZone(userId),
+      ]);
+      const awards = await this.registry.evaluate({ userId, isSuperuser, eventName, timeZone, payload }, earnedKeys);
       // Backfill is a retroactive catch-up, so it awards silently instead of flooding the user with notifications.
       const notify = eventName !== ACHIEVEMENT_EVENT_BACKFILL;
 
@@ -144,7 +150,7 @@ export class AchievementService implements OnModuleInit, OnModuleDestroy {
       }
 
       if (awarded > 0) {
-        await this.evaluateMetaBadges(userId, isSuperuser, earnedKeys, notify);
+        await this.evaluateMetaBadges(userId, isSuperuser, timeZone, earnedKeys, notify);
       }
 
       if (awarded > 0) {
@@ -250,9 +256,9 @@ export class AchievementService implements OnModuleInit, OnModuleDestroy {
     });
   }
 
-  private async evaluateMetaBadges(userId: number, isSuperuser: boolean, earnedKeys: Set<string>, notify: boolean): Promise<void> {
+  private async evaluateMetaBadges(userId: number, isSuperuser: boolean, timeZone: string, earnedKeys: Set<string>, notify: boolean): Promise<void> {
     const metaAwards = await this.registry.evaluate(
-      { userId, isSuperuser, eventName: ACHIEVEMENT_EVENT_ACHIEVEMENT_AWARDED, payload: { userId } },
+      { userId, isSuperuser, eventName: ACHIEVEMENT_EVENT_ACHIEVEMENT_AWARDED, timeZone, payload: { userId } },
       earnedKeys,
     );
     for (const award of metaAwards) {
@@ -268,6 +274,7 @@ export class AchievementService implements OnModuleInit, OnModuleDestroy {
   private async computeProgress(
     userId: number,
     isSuperuser: boolean,
+    timeZone: string,
     allAchievements: AchievementRow[],
     earnedMap: Map<string, UserAchievementRow>,
   ): Promise<Map<string, number>> {
@@ -287,7 +294,7 @@ export class AchievementService implements OnModuleInit, OnModuleDestroy {
       .map(([groupKey]) => groupKey);
 
     const progressEntries = await Promise.all(
-      groupsToFetch.map(async (groupKey) => [groupKey, await this.getProgressForGroup(userId, isSuperuser, groupKey)] as const),
+      groupsToFetch.map(async (groupKey) => [groupKey, await this.getProgressForGroup(userId, isSuperuser, timeZone, groupKey)] as const),
     );
 
     for (const [groupKey, progress] of progressEntries) {
@@ -304,7 +311,7 @@ export class AchievementService implements OnModuleInit, OnModuleDestroy {
 
     await Promise.all(
       singleBadgesToFetch.map(async (a) => {
-        const progress = await this.computeSingleBadgeProgress(userId, isSuperuser, a.key);
+        const progress = await this.computeSingleBadgeProgress(userId, isSuperuser, timeZone, a.key);
         if (progress !== null) {
           progressMap.set(a.key, progress);
         }
@@ -314,7 +321,7 @@ export class AchievementService implements OnModuleInit, OnModuleDestroy {
     return progressMap;
   }
 
-  private async computeSingleBadgeProgress(userId: number, isSuperuser: boolean, key: string): Promise<number | null> {
+  private async computeSingleBadgeProgress(userId: number, isSuperuser: boolean, timeZone: string, key: string): Promise<number | null> {
     switch (key) {
       case 'marathoner':
         return this.repo.getMaxSessionMinutes(userId);
@@ -340,13 +347,13 @@ export class AchievementService implements OnModuleInit, OnModuleDestroy {
       case 'note_keeper':
         return this.repo.countAnnotationsWithNotes(userId);
       case 'deep_dive_session':
-        return this.repo.countAnnotationsOnDay(userId, new Date());
+        return this.repo.countAnnotationsOnDay(userId, new Date(), timeZone);
       case 'monthly_reader_2': {
-        const now = new Date();
-        return this.repo.countBooksFinishedInMonth(userId, now.getUTCFullYear(), now.getUTCMonth() + 1);
+        const [year, month] = toDateKeyInTimeZone(new Date(), timeZone).split('-');
+        return this.repo.countBooksFinishedInMonth(userId, Number(year), Number(month));
       }
       case 'yearly_finisher_12':
-        return this.repo.countBooksFinishedInYear(userId, new Date().getUTCFullYear());
+        return this.repo.countBooksFinishedInYear(userId, getYearInTimeZone(new Date(), timeZone));
       case 'category_sweeper':
         return this.repo.countDistinctEarnedCategories(userId);
       case 'consistent_reader':
@@ -354,15 +361,14 @@ export class AchievementService implements OnModuleInit, OnModuleDestroy {
       case 'weekend_rhythm':
         return null;
       case 'seasonal_reader': {
-        const currentYear = new Date().getFullYear();
-        return this.repo.countDistinctSeasonsWithReading(userId, currentYear);
+        return this.repo.countDistinctSeasonsWithReading(userId, getYearInTimeZone(new Date(), timeZone));
       }
       case 'across_the_board':
         return this.repo.countDistinctRatingValues(userId);
       case 'power_hour':
         return this.repo.getMaxSessionPages(userId);
       case 'speed_reader':
-        return this.repo.getMaxPagesInADay(userId);
+        return this.repo.getMaxPagesInADay(userId, timeZone);
       case 'wordsmith':
         return this.repo.getMaxNoteLength(userId);
       case 'box_of_crayons':
@@ -376,7 +382,7 @@ export class AchievementService implements OnModuleInit, OnModuleDestroy {
     }
   }
 
-  private async getProgressForGroup(userId: number, isSuperuser: boolean, groupKey: string): Promise<number | null> {
+  private async getProgressForGroup(userId: number, isSuperuser: boolean, timeZone: string, groupKey: string): Promise<number | null> {
     switch (groupKey) {
       case 'books_finished':
         return this.repo.countFinishedBooks(userId);
@@ -393,7 +399,7 @@ export class AchievementService implements OnModuleInit, OnModuleDestroy {
       case 'polyglot':
         return this.repo.countDistinctLanguagesRead(userId);
       case 'streak':
-        return this.repo.getCurrentStreak(userId);
+        return this.repo.getCurrentStreak(userId, timeZone);
       case 'long_book':
         return this.repo.getMaxFinishedBookPageCount(userId);
       case 'critic':
diff --git a/server/src/modules/achievement/evaluators/dedication.evaluator.test.ts b/server/src/modules/achievement/evaluators/dedication.evaluator.test.ts
index 36a4d100f..523d39a0f 100644
--- a/server/src/modules/achievement/evaluators/dedication.evaluator.test.ts
+++ b/server/src/modules/achievement/evaluators/dedication.evaluator.test.ts
@@ -56,7 +56,13 @@ describe('DedicationEvaluator', () => {
     it('awards streak_1 at 7-day streak', async () => {
       repo.getCurrentStreak.mockResolvedValue(7);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: makeSessionPayload() as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
+          payload: makeSessionPayload() as never,
+        },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'streak_1' }));
@@ -65,7 +71,13 @@ describe('DedicationEvaluator', () => {
     it('awards multiple streak tiers at once', async () => {
       repo.getCurrentStreak.mockResolvedValue(35);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: makeSessionPayload() as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
+          payload: makeSessionPayload() as never,
+        },
         new Set(),
       );
       const keys = awards.map((a) => a.key);
@@ -79,7 +91,13 @@ describe('DedicationEvaluator', () => {
     it('awards year_round_reader at 12 months', async () => {
       repo.countDistinctMonthsWithReading.mockResolvedValue(12);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: makeSessionPayload() as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
+          payload: makeSessionPayload() as never,
+        },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'year_round_reader' }));
@@ -93,6 +111,7 @@ describe('DedicationEvaluator', () => {
         {
           userId: 1,
           isSuperuser: false,
+          timeZone: 'UTC',
           eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED,
           payload: { userId: 1, bookId: 5, newStatus: 'read', oldStatus: 'abandoned' } as never,
         },
@@ -107,7 +126,13 @@ describe('DedicationEvaluator', () => {
       const thirtyOneDaysAgo = new Date('2026-02-12T10:00:00Z');
       repo.getPreviousSessionEndedAt.mockResolvedValue(thirtyOneDaysAgo);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: makeSessionPayload() as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
+          payload: makeSessionPayload() as never,
+        },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'comeback_kid' }));
@@ -117,7 +142,13 @@ describe('DedicationEvaluator', () => {
       const fiveDaysAgo = new Date('2026-03-10T10:00:00Z');
       repo.getPreviousSessionEndedAt.mockResolvedValue(fiveDaysAgo);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: makeSessionPayload() as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
+          payload: makeSessionPayload() as never,
+        },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'comeback_kid')).toBeUndefined();
@@ -128,7 +159,13 @@ describe('DedicationEvaluator', () => {
     it('awards seasonal_reader when 4 distinct seasons have reading activity', async () => {
       repo.countDistinctSeasonsWithReading.mockResolvedValue(4);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: makeSessionPayload() as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
+          payload: makeSessionPayload() as never,
+        },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'seasonal_reader' }));
@@ -137,7 +174,13 @@ describe('DedicationEvaluator', () => {
     it('does not award seasonal_reader below 4 seasons', async () => {
       repo.countDistinctSeasonsWithReading.mockResolvedValue(3);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: makeSessionPayload() as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
+          payload: makeSessionPayload() as never,
+        },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'seasonal_reader')).toBeUndefined();
@@ -146,7 +189,13 @@ describe('DedicationEvaluator', () => {
     it('does not award seasonal_reader when already earned', async () => {
       repo.countDistinctSeasonsWithReading.mockResolvedValue(4);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: makeSessionPayload() as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
+          payload: makeSessionPayload() as never,
+        },
         new Set(['seasonal_reader']),
       );
       expect(awards.find((a) => a.key === 'seasonal_reader')).toBeUndefined();
@@ -155,7 +204,7 @@ describe('DedicationEvaluator', () => {
     it('awards seasonal_reader via backfill', async () => {
       repo.countDistinctSeasonsWithReading.mockResolvedValue(4);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'seasonal_reader' }));
@@ -166,7 +215,13 @@ describe('DedicationEvaluator', () => {
     it('awards perfect_month when user read every day in any calendar month', async () => {
       repo.hasReadEveryDayInAnyMonth.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: makeSessionPayload() as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
+          payload: makeSessionPayload() as never,
+        },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'perfect_month' }));
@@ -175,7 +230,13 @@ describe('DedicationEvaluator', () => {
     it('does not award perfect_month when no qualifying month', async () => {
       repo.hasReadEveryDayInAnyMonth.mockResolvedValue(false);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: makeSessionPayload() as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
+          payload: makeSessionPayload() as never,
+        },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'perfect_month')).toBeUndefined();
@@ -184,7 +245,13 @@ describe('DedicationEvaluator', () => {
     it('does not award perfect_month when already earned', async () => {
       repo.hasReadEveryDayInAnyMonth.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: makeSessionPayload() as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
+          payload: makeSessionPayload() as never,
+        },
         new Set(['perfect_month']),
       );
       expect(awards.find((a) => a.key === 'perfect_month')).toBeUndefined();
@@ -193,7 +260,7 @@ describe('DedicationEvaluator', () => {
     it('awards perfect_month via backfill', async () => {
       repo.hasReadEveryDayInAnyMonth.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'perfect_month' }));
@@ -204,7 +271,13 @@ describe('DedicationEvaluator', () => {
     it('awards consistent_reader when 30+ consecutive days with min 5 minutes each', async () => {
       repo.hasConsecutiveDaysWithMinReading.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: makeSessionPayload() as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
+          payload: makeSessionPayload() as never,
+        },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'consistent_reader' }));
@@ -213,7 +286,13 @@ describe('DedicationEvaluator', () => {
     it('does not award consistent_reader when condition not met', async () => {
       repo.hasConsecutiveDaysWithMinReading.mockResolvedValue(false);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: makeSessionPayload() as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
+          payload: makeSessionPayload() as never,
+        },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'consistent_reader')).toBeUndefined();
@@ -222,7 +301,13 @@ describe('DedicationEvaluator', () => {
     it('does not award consistent_reader when already earned', async () => {
       repo.hasConsecutiveDaysWithMinReading.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: makeSessionPayload() as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
+          payload: makeSessionPayload() as never,
+        },
         new Set(['consistent_reader']),
       );
       expect(awards.find((a) => a.key === 'consistent_reader')).toBeUndefined();
@@ -231,7 +316,7 @@ describe('DedicationEvaluator', () => {
     it('awards consistent_reader via backfill', async () => {
       repo.hasConsecutiveDaysWithMinReading.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'consistent_reader' }));
@@ -242,7 +327,13 @@ describe('DedicationEvaluator', () => {
     it('awards weekend_rhythm when 4+ consecutive weekends have reading', async () => {
       repo.hasConsecutiveWeekendsWithReading.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: makeSessionPayload() as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
+          payload: makeSessionPayload() as never,
+        },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'weekend_rhythm' }));
@@ -251,7 +342,13 @@ describe('DedicationEvaluator', () => {
     it('does not award weekend_rhythm when condition not met', async () => {
       repo.hasConsecutiveWeekendsWithReading.mockResolvedValue(false);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: makeSessionPayload() as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
+          payload: makeSessionPayload() as never,
+        },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'weekend_rhythm')).toBeUndefined();
@@ -260,7 +357,13 @@ describe('DedicationEvaluator', () => {
     it('does not award weekend_rhythm when already earned', async () => {
       repo.hasConsecutiveWeekendsWithReading.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: makeSessionPayload() as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
+          payload: makeSessionPayload() as never,
+        },
         new Set(['weekend_rhythm']),
       );
       expect(awards.find((a) => a.key === 'weekend_rhythm')).toBeUndefined();
@@ -269,7 +372,7 @@ describe('DedicationEvaluator', () => {
     it('awards weekend_rhythm via backfill', async () => {
       repo.hasConsecutiveWeekendsWithReading.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'weekend_rhythm' }));
@@ -283,6 +386,7 @@ describe('DedicationEvaluator', () => {
         {
           userId: 1,
           isSuperuser: false,
+          timeZone: 'UTC',
           eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
           payload: {
             userId: 1,
@@ -304,6 +408,7 @@ describe('DedicationEvaluator', () => {
         {
           userId: 1,
           isSuperuser: false,
+          timeZone: 'UTC',
           eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
           payload: {
             userId: 1,
@@ -324,6 +429,7 @@ describe('DedicationEvaluator', () => {
         {
           userId: 1,
           isSuperuser: false,
+          timeZone: 'UTC',
           eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
           payload: {
             userId: 1,
@@ -345,6 +451,7 @@ describe('DedicationEvaluator', () => {
         {
           userId: 1,
           isSuperuser: false,
+          timeZone: 'UTC',
           eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
           payload: {
             userId: 1,
@@ -364,7 +471,7 @@ describe('DedicationEvaluator', () => {
     it('awards weekend_warrior via backfill when user has a weekend marathon', async () => {
       repo.hasWeekendMarathon.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'weekend_warrior' }));
@@ -378,6 +485,7 @@ describe('DedicationEvaluator', () => {
         {
           userId: 1,
           isSuperuser: false,
+          timeZone: 'UTC',
           eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED,
           payload: { userId: 1, bookId: 5, newStatus: 'read', oldStatus: 'reading' } as never,
         },
@@ -392,6 +500,7 @@ describe('DedicationEvaluator', () => {
         {
           userId: 1,
           isSuperuser: false,
+          timeZone: 'UTC',
           eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED,
           payload: { userId: 1, bookId: 5, newStatus: 'read', oldStatus: 'reading' } as never,
         },
@@ -406,6 +515,7 @@ describe('DedicationEvaluator', () => {
         {
           userId: 1,
           isSuperuser: false,
+          timeZone: 'UTC',
           eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED,
           payload: { userId: 1, bookId: 5, newStatus: 'read', oldStatus: 'reading' } as never,
         },
@@ -417,7 +527,7 @@ describe('DedicationEvaluator', () => {
     it('awards yearly_finisher_12 via backfill', async () => {
       repo.countBooksFinishedInYear.mockResolvedValue(12);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'yearly_finisher_12' }));
@@ -428,7 +538,7 @@ describe('DedicationEvaluator', () => {
     it('awards comeback_kid via backfill when large session gap exists', async () => {
       repo.hasLargeGapBetweenAnySessions.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'comeback_kid' }));
@@ -437,7 +547,7 @@ describe('DedicationEvaluator', () => {
     it('does not award comeback_kid via backfill when no large gap', async () => {
       repo.hasLargeGapBetweenAnySessions.mockResolvedValue(false);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'comeback_kid')).toBeUndefined();
@@ -446,7 +556,7 @@ describe('DedicationEvaluator', () => {
     it('awards reborn via backfill when a previously abandoned book was finished', async () => {
       repo.hasAnyBookRebornFromAbandoned.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'reborn' }));
@@ -455,7 +565,7 @@ describe('DedicationEvaluator', () => {
     it('does not award reborn via backfill when no abandoned book was finished', async () => {
       repo.hasAnyBookRebornFromAbandoned.mockResolvedValue(false);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'reborn')).toBeUndefined();
diff --git a/server/src/modules/achievement/evaluators/dedication.evaluator.ts b/server/src/modules/achievement/evaluators/dedication.evaluator.ts
index f3867e789..85bf51630 100644
--- a/server/src/modules/achievement/evaluators/dedication.evaluator.ts
+++ b/server/src/modules/achievement/evaluators/dedication.evaluator.ts
@@ -1,6 +1,8 @@
 import { Injectable } from '@nestjs/common';
 import { toZonedTime } from 'date-fns-tz';
 
+import { getYearInTimeZone } from '../../../common/utils/timezone.utils';
+
 import { AchievementRepository } from '../achievement.repository';
 import {
   ACHIEVEMENT_EVENT_BACKFILL,
@@ -41,10 +43,10 @@ export class DedicationEvaluator implements IAchievementEvaluator {
 
     if (ctx.eventName === ACHIEVEMENT_EVENT_READING_SESSION_SAVED) {
       const payload = ctx.payload as unknown as ReadingSessionSavedPayload;
-      await this.evaluateStreakTiers(ctx.userId, earnedKeys, awards);
-      await this.evaluateYearRoundReader(ctx.userId, earnedKeys, awards);
+      await this.evaluateStreakTiers(ctx.userId, ctx.timeZone, earnedKeys, awards);
+      await this.evaluateYearRoundReader(ctx.userId, ctx.timeZone, earnedKeys, awards);
       await this.evaluateComebackKid(ctx.userId, payload, earnedKeys, awards);
-      await this.evaluateSeasonalReader(ctx.userId, earnedKeys, awards);
+      await this.evaluateSeasonalReader(ctx.userId, ctx.timeZone, earnedKeys, awards);
       await this.evaluatePerfectMonth(ctx.userId, earnedKeys, awards);
       await this.evaluateConsistentReader(ctx.userId, earnedKeys, awards);
       await this.evaluateWeekendRhythm(ctx.userId, earnedKeys, awards);
@@ -60,11 +62,11 @@ export class DedicationEvaluator implements IAchievementEvaluator {
     }
 
     if (ctx.eventName === ACHIEVEMENT_EVENT_BACKFILL) {
-      await this.evaluateStreakTiers(ctx.userId, earnedKeys, awards);
-      await this.evaluateYearRoundReader(ctx.userId, earnedKeys, awards);
+      await this.evaluateStreakTiers(ctx.userId, ctx.timeZone, earnedKeys, awards);
+      await this.evaluateYearRoundReader(ctx.userId, ctx.timeZone, earnedKeys, awards);
       await this.evaluateComebackKidBackfill(ctx.userId, earnedKeys, awards);
       await this.evaluateRebornBackfill(ctx.userId, earnedKeys, awards);
-      await this.evaluateSeasonalReader(ctx.userId, earnedKeys, awards);
+      await this.evaluateSeasonalReader(ctx.userId, ctx.timeZone, earnedKeys, awards);
       await this.evaluatePerfectMonth(ctx.userId, earnedKeys, awards);
       await this.evaluateConsistentReader(ctx.userId, earnedKeys, awards);
       await this.evaluateWeekendRhythm(ctx.userId, earnedKeys, awards);
@@ -75,11 +77,11 @@ export class DedicationEvaluator implements IAchievementEvaluator {
     return awards;
   }
 
-  private async evaluateStreakTiers(userId: number, earnedKeys: Set<string>, awards: AchievementAward[]): Promise<void> {
+  private async evaluateStreakTiers(userId: number, timeZone: string, earnedKeys: Set<string>, awards: AchievementAward[]): Promise<void> {
     const unearnedTiers = STREAK_TIERS.filter((t) => !earnedKeys.has(t.key));
     if (unearnedTiers.length === 0) return;
 
-    const streak = await this.repo.getCurrentStreak(userId);
+    const streak = await this.repo.getCurrentStreak(userId, timeZone);
 
     for (const tier of unearnedTiers) {
       if (streak >= tier.threshold) {
@@ -88,9 +90,9 @@ export class DedicationEvaluator implements IAchievementEvaluator {
     }
   }
 
-  private async evaluateYearRoundReader(userId: number, earnedKeys: Set<string>, awards: AchievementAward[]): Promise<void> {
+  private async evaluateYearRoundReader(userId: number, timeZone: string, earnedKeys: Set<string>, awards: AchievementAward[]): Promise<void> {
     if (earnedKeys.has('year_round_reader')) return;
-    const currentYear = new Date().getFullYear();
+    const currentYear = getYearInTimeZone(new Date(), timeZone);
     const months = await this.repo.countDistinctMonthsWithReading(userId, currentYear);
     if (months >= 12) {
       awards.push({ key: 'year_round_reader', context: { year: currentYear } });
@@ -138,9 +140,9 @@ export class DedicationEvaluator implements IAchievementEvaluator {
     }
   }
 
-  private async evaluateSeasonalReader(userId: number, earnedKeys: Set<string>, awards: AchievementAward[]): Promise<void> {
+  private async evaluateSeasonalReader(userId: number, timeZone: string, earnedKeys: Set<string>, awards: AchievementAward[]): Promise<void> {
     if (earnedKeys.has('seasonal_reader')) return;
-    const currentYear = new Date().getFullYear();
+    const currentYear = getYearInTimeZone(new Date(), timeZone);
     const seasonCount = await this.repo.countDistinctSeasonsWithReading(userId, currentYear);
     if (seasonCount >= SEASONAL_READER_THRESHOLD) {
       awards.push({ key: 'seasonal_reader', context: { year: currentYear, seasonCount } });
diff --git a/server/src/modules/achievement/evaluators/devices.evaluator.test.ts b/server/src/modules/achievement/evaluators/devices.evaluator.test.ts
index 530f7aa14..3268396be 100644
--- a/server/src/modules/achievement/evaluators/devices.evaluator.test.ts
+++ b/server/src/modules/achievement/evaluators/devices.evaluator.test.ts
@@ -21,10 +21,11 @@ describe('DevicesEvaluator', () => {
   const progressCtx = {
     userId: 1,
     isSuperuser: false,
+    timeZone: 'UTC',
     eventName: ACHIEVEMENT_EVENT_BOOK_PROGRESS_CHANGED,
     payload: { userId: 1, bookId: 5, progress: 50, source: 'kobo' } as never,
   };
-  const backfillCtx = { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never };
+  const backfillCtx = { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never };
 
   beforeEach(() => {
     repo = makeRepo();
@@ -85,7 +86,7 @@ describe('DevicesEvaluator', () => {
     it('short-circuits a web session when the user has no external device', async () => {
       repo.hasAnyExternalDevice.mockResolvedValue(false);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards).toHaveLength(0);
diff --git a/server/src/modules/achievement/evaluators/evaluator.interface.ts b/server/src/modules/achievement/evaluators/evaluator.interface.ts
index 40437a45b..857e994dd 100644
--- a/server/src/modules/achievement/evaluators/evaluator.interface.ts
+++ b/server/src/modules/achievement/evaluators/evaluator.interface.ts
@@ -7,6 +7,7 @@ export interface EvaluationContext {
   userId: number;
   isSuperuser: boolean;
   eventName: string;
+  timeZone: string;
   payload: Record<string, unknown>;
 }
 
diff --git a/server/src/modules/achievement/evaluators/exploration.evaluator.test.ts b/server/src/modules/achievement/evaluators/exploration.evaluator.test.ts
index 6b29c42f1..74e54fe37 100644
--- a/server/src/modules/achievement/evaluators/exploration.evaluator.test.ts
+++ b/server/src/modules/achievement/evaluators/exploration.evaluator.test.ts
@@ -45,6 +45,7 @@ describe('ExplorationEvaluator', () => {
       {
         userId: 1,
         isSuperuser: false,
+        timeZone: 'UTC',
         eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED,
         payload: makeStatusPayload({ newStatus: 'reading' }) as never,
       },
@@ -57,7 +58,7 @@ describe('ExplorationEvaluator', () => {
     it('awards tier 1 at 5 genres', async () => {
       repo.countDistinctGenresRead.mockResolvedValue(5);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'genre_explorer_1' }));
@@ -68,7 +69,7 @@ describe('ExplorationEvaluator', () => {
     it('awards tier 1 at 2 languages', async () => {
       repo.countDistinctLanguagesRead.mockResolvedValue(2);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'polyglot_1' }));
@@ -79,7 +80,7 @@ describe('ExplorationEvaluator', () => {
     it('awards old_soul for pre-1900 book', async () => {
       repo.getBookPublishedYear.mockResolvedValue(1850);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'old_soul' }));
@@ -88,7 +89,7 @@ describe('ExplorationEvaluator', () => {
     it('does not award old_soul for 1900+ book', async () => {
       repo.getBookPublishedYear.mockResolvedValue(1901);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'old_soul')).toBeUndefined();
@@ -99,7 +100,7 @@ describe('ExplorationEvaluator', () => {
     it('awards new_release for current year book', async () => {
       repo.getBookPublishedYear.mockResolvedValue(new Date().getFullYear());
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'new_release' }));
@@ -110,7 +111,7 @@ describe('ExplorationEvaluator', () => {
     it('awards century_span at 3+ centuries', async () => {
       repo.countDistinctCenturiesRead.mockResolvedValue(3);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'century_span' }));
@@ -121,7 +122,7 @@ describe('ExplorationEvaluator', () => {
     it('awards author_deep_dive at 5+ books from same author', async () => {
       repo.maxBooksPerAuthor.mockResolvedValue(5);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'author_deep_dive' }));
@@ -132,7 +133,7 @@ describe('ExplorationEvaluator', () => {
     it('awards decade_sampler when 5+ distinct decades read', async () => {
       repo.countDistinctDecadesRead.mockResolvedValue(5);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'decade_sampler' }));
@@ -141,7 +142,7 @@ describe('ExplorationEvaluator', () => {
     it('does not award decade_sampler below 5 decades', async () => {
       repo.countDistinctDecadesRead.mockResolvedValue(4);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'decade_sampler')).toBeUndefined();
@@ -150,7 +151,7 @@ describe('ExplorationEvaluator', () => {
     it('does not award decade_sampler when already earned', async () => {
       repo.countDistinctDecadesRead.mockResolvedValue(10);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(['decade_sampler']),
       );
       expect(awards.find((a) => a.key === 'decade_sampler')).toBeUndefined();
@@ -161,7 +162,7 @@ describe('ExplorationEvaluator', () => {
     it('awards short_story_fan when 5+ short books finished', async () => {
       repo.countFinishedBooksByMaxPageCount.mockResolvedValue(5);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'short_story_fan' }));
@@ -170,7 +171,7 @@ describe('ExplorationEvaluator', () => {
     it('does not award short_story_fan below 5 short books', async () => {
       repo.countFinishedBooksByMaxPageCount.mockResolvedValue(4);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'short_story_fan')).toBeUndefined();
@@ -179,7 +180,7 @@ describe('ExplorationEvaluator', () => {
     it('does not award short_story_fan when already earned', async () => {
       repo.countFinishedBooksByMaxPageCount.mockResolvedValue(10);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(['short_story_fan']),
       );
       expect(awards.find((a) => a.key === 'short_story_fan')).toBeUndefined();
@@ -191,7 +192,7 @@ describe('ExplorationEvaluator', () => {
       repo.hasFinishedBookUnderPages.mockResolvedValue(true);
       repo.hasFinishedBookOverPages.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'thick_and_thin' }));
@@ -201,7 +202,7 @@ describe('ExplorationEvaluator', () => {
       repo.hasFinishedBookUnderPages.mockResolvedValue(true);
       repo.hasFinishedBookOverPages.mockResolvedValue(false);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'thick_and_thin')).toBeUndefined();
@@ -211,7 +212,7 @@ describe('ExplorationEvaluator', () => {
       repo.hasFinishedBookUnderPages.mockResolvedValue(false);
       repo.hasFinishedBookOverPages.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'thick_and_thin')).toBeUndefined();
@@ -220,7 +221,7 @@ describe('ExplorationEvaluator', () => {
     it('short-circuits when no thin book - does not query thick books', async () => {
       repo.hasFinishedBookUnderPages.mockResolvedValue(false);
       await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(repo.hasFinishedBookOverPages).not.toHaveBeenCalled();
@@ -230,7 +231,7 @@ describe('ExplorationEvaluator', () => {
       repo.hasFinishedBookUnderPages.mockResolvedValue(true);
       repo.hasFinishedBookOverPages.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(['thick_and_thin']),
       );
       expect(awards.find((a) => a.key === 'thick_and_thin')).toBeUndefined();
@@ -241,7 +242,7 @@ describe('ExplorationEvaluator', () => {
     it('awards trilogy_master when a 3-book series is completed', async () => {
       repo.hasCompletedSeriesOfSize.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'trilogy_master' }));
@@ -250,7 +251,7 @@ describe('ExplorationEvaluator', () => {
     it('does not award trilogy_master when no 3-book series completed', async () => {
       repo.hasCompletedSeriesOfSize.mockResolvedValue(false);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'trilogy_master')).toBeUndefined();
@@ -259,7 +260,7 @@ describe('ExplorationEvaluator', () => {
     it('passes size=3 to repo method', async () => {
       repo.hasCompletedSeriesOfSize.mockResolvedValue(true);
       await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(repo.hasCompletedSeriesOfSize).toHaveBeenCalledWith(1, 3);
@@ -268,7 +269,7 @@ describe('ExplorationEvaluator', () => {
     it('does not award trilogy_master when already earned', async () => {
       repo.hasCompletedSeriesOfSize.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(['trilogy_master']),
       );
       expect(awards.find((a) => a.key === 'trilogy_master')).toBeUndefined();
@@ -279,7 +280,7 @@ describe('ExplorationEvaluator', () => {
     it('awards genre_devotee when 10+ books in same genre', async () => {
       repo.maxBooksPerGenre.mockResolvedValue(10);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'genre_devotee' }));
@@ -288,7 +289,7 @@ describe('ExplorationEvaluator', () => {
     it('does not award genre_devotee below 10 books in a genre', async () => {
       repo.maxBooksPerGenre.mockResolvedValue(9);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'genre_devotee')).toBeUndefined();
@@ -297,7 +298,7 @@ describe('ExplorationEvaluator', () => {
     it('does not award genre_devotee when already earned', async () => {
       repo.maxBooksPerGenre.mockResolvedValue(20);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(['genre_devotee']),
       );
       expect(awards.find((a) => a.key === 'genre_devotee')).toBeUndefined();
@@ -305,7 +306,7 @@ describe('ExplorationEvaluator', () => {
   });
 
   describe('backfill for new exploration badges', () => {
-    const backfillCtx = { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never };
+    const backfillCtx = { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never };
 
     it('awards decade_sampler in backfill', async () => {
       repo.countDistinctDecadesRead.mockResolvedValue(5);
diff --git a/server/src/modules/achievement/evaluators/exploration.evaluator.ts b/server/src/modules/achievement/evaluators/exploration.evaluator.ts
index e949af3f0..8ce173ac2 100644
--- a/server/src/modules/achievement/evaluators/exploration.evaluator.ts
+++ b/server/src/modules/achievement/evaluators/exploration.evaluator.ts
@@ -1,5 +1,6 @@
 import { Injectable } from '@nestjs/common';
 
+import { getYearInTimeZone } from '../../../common/utils/timezone.utils';
 import { AchievementRepository } from '../achievement.repository';
 import { ACHIEVEMENT_EVENT_BACKFILL, ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, type BookStatusChangedPayload } from '../achievement-events.service';
 import type { AchievementAward, EvaluationContext, IAchievementEvaluator } from './evaluator.interface';
@@ -36,7 +37,7 @@ export class ExplorationEvaluator implements IAchievementEvaluator {
 
   async evaluate(ctx: EvaluationContext, earnedKeys: Set<string>): Promise<AchievementAward[]> {
     if (ctx.eventName === ACHIEVEMENT_EVENT_BACKFILL) {
-      return this.evaluateBackfill(ctx.userId, earnedKeys);
+      return this.evaluateBackfill(ctx.userId, ctx.timeZone, earnedKeys);
     }
 
     const payload = ctx.payload as unknown as BookStatusChangedPayload;
@@ -47,7 +48,7 @@ export class ExplorationEvaluator implements IAchievementEvaluator {
     await this.evaluateGenreExplorerTiers(ctx.userId, earnedKeys, awards);
     await this.evaluatePolyglotTiers(ctx.userId, earnedKeys, awards);
     await this.evaluateOldSoul(ctx.userId, payload.bookId, earnedKeys, awards);
-    await this.evaluateNewRelease(ctx.userId, payload.bookId, earnedKeys, awards);
+    await this.evaluateNewRelease(ctx.userId, ctx.timeZone, payload.bookId, earnedKeys, awards);
     await this.evaluateCenturySpan(ctx.userId, earnedKeys, awards);
     await this.evaluateAuthorDeepDive(ctx.userId, earnedKeys, awards);
     await this.evaluateDecadeSampler(ctx.userId, earnedKeys, awards);
@@ -59,13 +60,13 @@ export class ExplorationEvaluator implements IAchievementEvaluator {
     return awards;
   }
 
-  private async evaluateBackfill(userId: number, earnedKeys: Set<string>): Promise<AchievementAward[]> {
+  private async evaluateBackfill(userId: number, timeZone: string, earnedKeys: Set<string>): Promise<AchievementAward[]> {
     const awards: AchievementAward[] = [];
 
     await this.evaluateGenreExplorerTiers(userId, earnedKeys, awards);
     await this.evaluatePolyglotTiers(userId, earnedKeys, awards);
     await this.evaluateOldSoulBackfill(userId, earnedKeys, awards);
-    await this.evaluateNewReleaseBackfill(userId, earnedKeys, awards);
+    await this.evaluateNewReleaseBackfill(userId, timeZone, earnedKeys, awards);
     await this.evaluateCenturySpan(userId, earnedKeys, awards);
     await this.evaluateAuthorDeepDive(userId, earnedKeys, awards);
     await this.evaluateDecadeSampler(userId, earnedKeys, awards);
@@ -112,10 +113,16 @@ export class ExplorationEvaluator implements IAchievementEvaluator {
     }
   }
 
-  private async evaluateNewRelease(userId: number, bookId: number, earnedKeys: Set<string>, awards: AchievementAward[]): Promise<void> {
+  private async evaluateNewRelease(
+    userId: number,
+    timeZone: string,
+    bookId: number,
+    earnedKeys: Set<string>,
+    awards: AchievementAward[],
+  ): Promise<void> {
     if (earnedKeys.has('new_release')) return;
     const publishedYear = await this.repo.getBookPublishedYear(bookId);
-    const currentYear = new Date().getFullYear();
+    const currentYear = getYearInTimeZone(new Date(), timeZone);
     if (publishedYear !== null && publishedYear === currentYear) {
       const bookTitle = await this.repo.getBookTitle(bookId);
       awards.push({ key: 'new_release', context: { bookId, bookTitle, publishedYear } });
@@ -188,9 +195,9 @@ export class ExplorationEvaluator implements IAchievementEvaluator {
     }
   }
 
-  private async evaluateNewReleaseBackfill(userId: number, earnedKeys: Set<string>, awards: AchievementAward[]): Promise<void> {
+  private async evaluateNewReleaseBackfill(userId: number, timeZone: string, earnedKeys: Set<string>, awards: AchievementAward[]): Promise<void> {
     if (earnedKeys.has('new_release')) return;
-    const currentYear = new Date().getFullYear();
+    const currentYear = getYearInTimeZone(new Date(), timeZone);
     const hasBook = await this.repo.hasFinishedBookPublishedInYear(userId, currentYear);
     if (hasBook) {
       awards.push({ key: 'new_release', context: { publishedYear: currentYear } });
diff --git a/server/src/modules/achievement/evaluators/library.evaluator.test.ts b/server/src/modules/achievement/evaluators/library.evaluator.test.ts
index 6b3689cd1..fbdcef23b 100644
--- a/server/src/modules/achievement/evaluators/library.evaluator.test.ts
+++ b/server/src/modules/achievement/evaluators/library.evaluator.test.ts
@@ -48,6 +48,7 @@ describe('LibraryEvaluator', () => {
         {
           userId: 1,
           isSuperuser: false,
+          timeZone: 'UTC',
           eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED,
           payload: { userId: 1, bookId: 1, newStatus: 'read', oldStatus: 'reading' },
         },
@@ -62,6 +63,7 @@ describe('LibraryEvaluator', () => {
         {
           userId: 1,
           isSuperuser: false,
+          timeZone: 'UTC',
           eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED,
           payload: { userId: 1, bookId: 1, newStatus: 'reading', oldStatus: 'unread' },
         },
@@ -73,7 +75,13 @@ describe('LibraryEvaluator', () => {
     it('awards tiers on library catalog changes without requiring read status transitions', async () => {
       repo.countAccessibleBooks.mockResolvedValue(250);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_LIBRARY_CATALOG_CHANGED, payload: { userId: 1, libraryId: 10 } as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_LIBRARY_CATALOG_CHANGED,
+          payload: { userId: 1, libraryId: 10 } as never,
+        },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'library_builder_1' }));
@@ -85,7 +93,7 @@ describe('LibraryEvaluator', () => {
     it('awards annotator_1 at 10 annotations', async () => {
       repo.countAnnotations.mockResolvedValue(10);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1 } },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1 } },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'annotator_1' }));
@@ -94,7 +102,7 @@ describe('LibraryEvaluator', () => {
     it('does not include bookmarked (now handled by MilestonesEvaluator)', async () => {
       repo.countAnnotations.mockResolvedValue(1);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1 } },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1 } },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'bookmarked')).toBeUndefined();
@@ -108,6 +116,7 @@ describe('LibraryEvaluator', () => {
         {
           userId: 1,
           isSuperuser: false,
+          timeZone: 'UTC',
           eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED,
           payload: { userId: 1, bookId: 1, newStatus: 'read', oldStatus: 'reading' },
         },
@@ -119,7 +128,13 @@ describe('LibraryEvaluator', () => {
     it('awards multi_format on library catalog changes', async () => {
       repo.countDistinctFormats.mockResolvedValue(3);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_LIBRARY_CATALOG_CHANGED, payload: { userId: 1, libraryId: 2 } as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_LIBRARY_CATALOG_CHANGED,
+          payload: { userId: 1, libraryId: 2 } as never,
+        },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'multi_format' }));
@@ -130,7 +145,7 @@ describe('LibraryEvaluator', () => {
     it('awards curator at 10 collections', async () => {
       repo.countCollections.mockResolvedValue(10);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_COLLECTION_CREATED, payload: { userId: 1 } },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_COLLECTION_CREATED, payload: { userId: 1 } },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'curator' }));
@@ -139,7 +154,7 @@ describe('LibraryEvaluator', () => {
     it('does not award curator below 10', async () => {
       repo.countCollections.mockResolvedValue(9);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_COLLECTION_CREATED, payload: { userId: 1 } },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_COLLECTION_CREATED, payload: { userId: 1 } },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'curator')).toBeUndefined();
@@ -150,7 +165,7 @@ describe('LibraryEvaluator', () => {
     it('awards note_keeper when 20+ annotations have notes', async () => {
       repo.countAnnotationsWithNotes.mockResolvedValue(25);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1 } },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1 } },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'note_keeper' }));
@@ -159,7 +174,7 @@ describe('LibraryEvaluator', () => {
     it('does not award note_keeper below 20', async () => {
       repo.countAnnotationsWithNotes.mockResolvedValue(24);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1 } },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1 } },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'note_keeper')).toBeUndefined();
@@ -168,7 +183,7 @@ describe('LibraryEvaluator', () => {
     it('does not award note_keeper when already earned', async () => {
       repo.countAnnotationsWithNotes.mockResolvedValue(50);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1 } },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1 } },
         new Set(['note_keeper']),
       );
       expect(awards.find((a) => a.key === 'note_keeper')).toBeUndefined();
@@ -177,7 +192,7 @@ describe('LibraryEvaluator', () => {
     it('awards note_keeper via backfill', async () => {
       repo.countAnnotationsWithNotes.mockResolvedValue(25);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'note_keeper' }));
@@ -188,7 +203,7 @@ describe('LibraryEvaluator', () => {
     it('awards deep_dive_session when 10+ annotations created today', async () => {
       repo.countAnnotationsOnDay.mockResolvedValue(10);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1 } },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1 } },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'deep_dive_session' }));
@@ -197,7 +212,7 @@ describe('LibraryEvaluator', () => {
     it('does not award deep_dive_session below 10 today', async () => {
       repo.countAnnotationsOnDay.mockResolvedValue(9);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1 } },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1 } },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'deep_dive_session')).toBeUndefined();
@@ -206,7 +221,7 @@ describe('LibraryEvaluator', () => {
     it('does not award deep_dive_session when already earned', async () => {
       repo.countAnnotationsOnDay.mockResolvedValue(15);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1 } },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1 } },
         new Set(['deep_dive_session']),
       );
       expect(awards.find((a) => a.key === 'deep_dive_session')).toBeUndefined();
@@ -215,7 +230,7 @@ describe('LibraryEvaluator', () => {
     it('awards deep_dive_session via backfill', async () => {
       repo.hasAnyDayWithAnnotationCount.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'deep_dive_session' }));
@@ -224,7 +239,7 @@ describe('LibraryEvaluator', () => {
     it('does not award deep_dive_session via backfill when no qualifying day', async () => {
       repo.hasAnyDayWithAnnotationCount.mockResolvedValue(false);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'deep_dive_session')).toBeUndefined();
@@ -235,7 +250,13 @@ describe('LibraryEvaluator', () => {
     it('awards wordsmith for a note longer than 280 chars', async () => {
       repo.getAnnotationNoteLength.mockResolvedValue(300);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1, annotationId: 9 } },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED,
+          payload: { userId: 1, bookId: 1, annotationId: 9 },
+        },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'wordsmith' }));
@@ -244,7 +265,13 @@ describe('LibraryEvaluator', () => {
     it('does not award wordsmith for a note of exactly 280 chars', async () => {
       repo.getAnnotationNoteLength.mockResolvedValue(280);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1, annotationId: 9 } },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED,
+          payload: { userId: 1, bookId: 1, annotationId: 9 },
+        },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'wordsmith')).toBeUndefined();
@@ -253,7 +280,13 @@ describe('LibraryEvaluator', () => {
     it('does not award wordsmith when the annotation has no note', async () => {
       repo.getAnnotationNoteLength.mockResolvedValue(null);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1, annotationId: 9 } },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED,
+          payload: { userId: 1, bookId: 1, annotationId: 9 },
+        },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'wordsmith')).toBeUndefined();
@@ -262,7 +295,7 @@ describe('LibraryEvaluator', () => {
     it('awards wordsmith via backfill', async () => {
       repo.getMaxNoteLength.mockResolvedValue(500);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'wordsmith' }));
@@ -273,7 +306,13 @@ describe('LibraryEvaluator', () => {
     it('awards box_of_crayons when all 5 colors are used', async () => {
       repo.countDistinctColors.mockResolvedValue(5);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1, annotationId: 9 } },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED,
+          payload: { userId: 1, bookId: 1, annotationId: 9 },
+        },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'box_of_crayons' }));
@@ -282,7 +321,13 @@ describe('LibraryEvaluator', () => {
     it('does not award box_of_crayons with only 4 colors', async () => {
       repo.countDistinctColors.mockResolvedValue(4);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 1, annotationId: 9 } },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED,
+          payload: { userId: 1, bookId: 1, annotationId: 9 },
+        },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'box_of_crayons')).toBeUndefined();
@@ -291,7 +336,7 @@ describe('LibraryEvaluator', () => {
     it('awards box_of_crayons via backfill', async () => {
       repo.countDistinctColors.mockResolvedValue(5);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'box_of_crayons' }));
diff --git a/server/src/modules/achievement/evaluators/library.evaluator.ts b/server/src/modules/achievement/evaluators/library.evaluator.ts
index af7ce0016..0ca81eaf9 100644
--- a/server/src/modules/achievement/evaluators/library.evaluator.ts
+++ b/server/src/modules/achievement/evaluators/library.evaluator.ts
@@ -52,7 +52,7 @@ export class LibraryEvaluator implements IAchievementEvaluator {
       const payload = ctx.payload as unknown as AnnotationCreatedPayload;
       await this.evaluateAnnotatorTiers(ctx.userId, earnedKeys, awards);
       await this.evaluateNoteKeeper(ctx.userId, earnedKeys, awards);
-      await this.evaluateDeepDiveSession(ctx.userId, payload, earnedKeys, awards);
+      await this.evaluateDeepDiveSession(ctx.userId, ctx.timeZone, payload, earnedKeys, awards);
       await this.evaluateWordsmith(ctx.userId, payload, earnedKeys, awards);
       await this.evaluateBoxOfCrayons(ctx.userId, earnedKeys, awards);
     }
@@ -145,13 +145,13 @@ export class LibraryEvaluator implements IAchievementEvaluator {
 
   private async evaluateDeepDiveSession(
     userId: number,
+    timeZone: string,
     payload: AnnotationCreatedPayload,
     earnedKeys: Set<string>,
     awards: AchievementAward[],
   ): Promise<void> {
     if (earnedKeys.has('deep_dive_session')) return;
-    const today = new Date();
-    const count = await this.repo.countAnnotationsOnDay(userId, today);
+    const count = await this.repo.countAnnotationsOnDay(userId, new Date(), timeZone);
     if (count >= DEEP_DIVE_SESSION_THRESHOLD) {
       awards.push({ key: 'deep_dive_session', context: { count, bookId: payload.bookId } });
     }
diff --git a/server/src/modules/achievement/evaluators/milestones.evaluator.test.ts b/server/src/modules/achievement/evaluators/milestones.evaluator.test.ts
index 44c5bc213..fea48883e 100644
--- a/server/src/modules/achievement/evaluators/milestones.evaluator.test.ts
+++ b/server/src/modules/achievement/evaluators/milestones.evaluator.test.ts
@@ -46,7 +46,13 @@ describe('MilestonesEvaluator', () => {
   describe('bookmarked', () => {
     it('awards bookmarked on annotation creation', async () => {
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED, payload: { userId: 1, bookId: 5 } as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_ANNOTATION_CREATED,
+          payload: { userId: 1, bookId: 5 } as never,
+        },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'bookmarked' }));
@@ -189,7 +195,7 @@ describe('MilestonesEvaluator', () => {
     it('awards first_series via backfill', async () => {
       repo.hasFinishedBookInSeries.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'first_series' }));
@@ -200,7 +206,13 @@ describe('MilestonesEvaluator', () => {
     it('awards category_sweeper when all 4 categories have at least one badge earned', async () => {
       repo.countDistinctEarnedCategories.mockResolvedValue(4);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_ACHIEVEMENT_AWARDED, payload: { userId: 1, keys: ['some_key'] } as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_ACHIEVEMENT_AWARDED,
+          payload: { userId: 1, keys: ['some_key'] } as never,
+        },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'category_sweeper' }));
@@ -209,7 +221,13 @@ describe('MilestonesEvaluator', () => {
     it('does not award category_sweeper below 4 categories', async () => {
       repo.countDistinctEarnedCategories.mockResolvedValue(3);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_ACHIEVEMENT_AWARDED, payload: { userId: 1, keys: ['some_key'] } as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_ACHIEVEMENT_AWARDED,
+          payload: { userId: 1, keys: ['some_key'] } as never,
+        },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'category_sweeper')).toBeUndefined();
@@ -218,7 +236,13 @@ describe('MilestonesEvaluator', () => {
     it('does not award category_sweeper when already earned', async () => {
       repo.countDistinctEarnedCategories.mockResolvedValue(4);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_ACHIEVEMENT_AWARDED, payload: { userId: 1, keys: ['some_key'] } as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_ACHIEVEMENT_AWARDED,
+          payload: { userId: 1, keys: ['some_key'] } as never,
+        },
         new Set(['category_sweeper']),
       );
       expect(awards.find((a) => a.key === 'category_sweeper')).toBeUndefined();
@@ -227,7 +251,7 @@ describe('MilestonesEvaluator', () => {
     it('awards category_sweeper via backfill', async () => {
       repo.countDistinctEarnedCategories.mockResolvedValue(4);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'category_sweeper' }));
@@ -236,7 +260,7 @@ describe('MilestonesEvaluator', () => {
     it('does not award category_sweeper via backfill below 4 categories', async () => {
       repo.countDistinctEarnedCategories.mockResolvedValue(3);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'category_sweeper')).toBeUndefined();
@@ -247,7 +271,7 @@ describe('MilestonesEvaluator', () => {
     it('awards bookmarked via backfill when user has annotations', async () => {
       repo.countAnnotations.mockResolvedValue(3);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'bookmarked' }));
@@ -256,7 +280,7 @@ describe('MilestonesEvaluator', () => {
     it('does not award bookmarked via backfill when no annotations', async () => {
       repo.countAnnotations.mockResolvedValue(0);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'bookmarked')).toBeUndefined();
@@ -265,7 +289,7 @@ describe('MilestonesEvaluator', () => {
     it('awards new_year_reader via backfill when a Jan 1 session exists', async () => {
       repo.hasSessionOnJanFirst.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'new_year_reader' }));
@@ -338,7 +362,7 @@ describe('MilestonesEvaluator', () => {
     it('awards dnf_self_aware via backfill when an abandoned book exists', async () => {
       repo.hasAbandonedBook.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'dnf_self_aware' }));
diff --git a/server/src/modules/achievement/evaluators/rating.evaluator.test.ts b/server/src/modules/achievement/evaluators/rating.evaluator.test.ts
index 48d69f4e1..fea08b016 100644
--- a/server/src/modules/achievement/evaluators/rating.evaluator.test.ts
+++ b/server/src/modules/achievement/evaluators/rating.evaluator.test.ts
@@ -19,7 +19,7 @@ function makeRatingPayload(overrides: Partial<Record<string, unknown>> = {}) {
 describe('RatingEvaluator', () => {
   let evaluator: RatingEvaluator;
   let repo: ReturnType<typeof makeRepo>;
-  const backfillCtx = { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never };
+  const backfillCtx = { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never };
 
   beforeEach(() => {
     repo = makeRepo();
@@ -27,7 +27,7 @@ describe('RatingEvaluator', () => {
   });
 
   function ratingCtx(payload = makeRatingPayload()) {
-    return { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_RATING_CHANGED, payload: payload as never };
+    return { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_RATING_CHANGED, payload: payload as never };
   }
 
   it('supports rating-changed and backfill events', () => {
diff --git a/server/src/modules/achievement/evaluators/reading.evaluator.test.ts b/server/src/modules/achievement/evaluators/reading.evaluator.test.ts
index 6b35b9c11..7c421b5fd 100644
--- a/server/src/modules/achievement/evaluators/reading.evaluator.test.ts
+++ b/server/src/modules/achievement/evaluators/reading.evaluator.test.ts
@@ -59,7 +59,7 @@ function makeStatusPayload(overrides: Partial<Record<string, unknown>> = {}) {
 describe('ReadingEvaluator', () => {
   let evaluator: ReadingEvaluator;
   let repo: ReturnType<typeof makeRepo>;
-  const backfillCtx = { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never };
+  const backfillCtx = { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BACKFILL, payload: { userId: 1 } as never };
 
   beforeEach(() => {
     repo = makeRepo();
@@ -77,7 +77,7 @@ describe('ReadingEvaluator', () => {
     it('awards tier 1 when 1 book finished', async () => {
       repo.countFinishedBooks.mockResolvedValue(1);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'books_finished_1' }));
@@ -86,7 +86,7 @@ describe('ReadingEvaluator', () => {
     it('awards multiple tiers at once when count is high enough', async () => {
       repo.countFinishedBooks.mockResolvedValue(55);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       const keys = awards.map((a) => a.key);
@@ -100,7 +100,7 @@ describe('ReadingEvaluator', () => {
       repo.countFinishedBooks.mockResolvedValue(55);
       const earned = new Set(['books_finished_1', 'books_finished_2']);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         earned,
       );
       const keys = awards.map((a) => a.key);
@@ -115,6 +115,7 @@ describe('ReadingEvaluator', () => {
         {
           userId: 1,
           isSuperuser: false,
+          timeZone: 'UTC',
           eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED,
           payload: makeStatusPayload({ newStatus: 'reading' }) as never,
         },
@@ -129,7 +130,7 @@ describe('ReadingEvaluator', () => {
       repo.countFinishedBooks.mockResolvedValue(1);
       repo.sumPagesRead.mockResolvedValue(500);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'pages_read_1' }));
@@ -138,7 +139,13 @@ describe('ReadingEvaluator', () => {
     it('awards pages_read tiers on reading session events', async () => {
       repo.sumPagesRead.mockResolvedValue(500);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: makeSessionPayload() as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
+          payload: makeSessionPayload() as never,
+        },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'pages_read_1' }));
@@ -149,7 +156,13 @@ describe('ReadingEvaluator', () => {
     it('awards hours_read_1 at 10 hours', async () => {
       repo.sumReadingHours.mockResolvedValue(10);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED, payload: makeSessionPayload() as never },
+        {
+          userId: 1,
+          isSuperuser: false,
+          timeZone: 'UTC',
+          eventName: ACHIEVEMENT_EVENT_READING_SESSION_SAVED,
+          payload: makeSessionPayload() as never,
+        },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'hours_read_1' }));
@@ -303,7 +316,7 @@ describe('ReadingEvaluator', () => {
       repo.countFinishedBooks.mockResolvedValue(1);
       repo.getBookPageCount.mockResolvedValue(320);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'long_book_1' }));
@@ -314,7 +327,7 @@ describe('ReadingEvaluator', () => {
       repo.countFinishedBooks.mockResolvedValue(1);
       repo.getBookPageCount.mockResolvedValue(550);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'long_book_1' }));
@@ -327,7 +340,7 @@ describe('ReadingEvaluator', () => {
       repo.countFinishedBooks.mockResolvedValue(1);
       repo.getBookPageCount.mockResolvedValue(780);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'long_book_1' }));
@@ -340,7 +353,7 @@ describe('ReadingEvaluator', () => {
       repo.countFinishedBooks.mockResolvedValue(1);
       repo.getBookPageCount.mockResolvedValue(1100);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'long_book_1' }));
@@ -353,7 +366,7 @@ describe('ReadingEvaluator', () => {
       repo.countFinishedBooks.mockResolvedValue(1);
       repo.getBookPageCount.mockResolvedValue(1200);
       await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(repo.getBookPageCount).toHaveBeenCalledOnce();
@@ -365,7 +378,7 @@ describe('ReadingEvaluator', () => {
       repo.countFinishedBooks.mockResolvedValue(1);
       repo.wasBookStartedAndFinishedOnSameDay.mockResolvedValue(true);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'sprint' }));
@@ -377,7 +390,7 @@ describe('ReadingEvaluator', () => {
       repo.countFinishedBooks.mockResolvedValue(3);
       repo.countBooksFinishedInDateRange.mockResolvedValue(3);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'binge_reader' }));
@@ -460,7 +473,7 @@ describe('ReadingEvaluator', () => {
       const finishedAt = new Date('2025-04-15T00:00:00Z'); // 104 days later
       repo.getBookStartedAndFinishedAt.mockResolvedValue({ startedAt, finishedAt });
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'slow_burn' }));
@@ -471,7 +484,7 @@ describe('ReadingEvaluator', () => {
       const finishedAt = new Date('2025-04-01T00:00:00Z'); // exactly 90 days
       repo.getBookStartedAndFinishedAt.mockResolvedValue({ startedAt, finishedAt });
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'slow_burn')).toBeUndefined();
@@ -480,7 +493,7 @@ describe('ReadingEvaluator', () => {
     it('does not award slow_burn when dates are missing', async () => {
       repo.getBookStartedAndFinishedAt.mockResolvedValue({ startedAt: null, finishedAt: null });
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'slow_burn')).toBeUndefined();
@@ -489,7 +502,7 @@ describe('ReadingEvaluator', () => {
     it('does not award slow_burn when status book info returns null', async () => {
       repo.getBookStartedAndFinishedAt.mockResolvedValue(null);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'slow_burn')).toBeUndefined();
@@ -500,7 +513,7 @@ describe('ReadingEvaluator', () => {
       const finishedAt = new Date('2025-05-01T00:00:00Z');
       repo.getBookStartedAndFinishedAt.mockResolvedValue({ startedAt, finishedAt });
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(['slow_burn']),
       );
       expect(awards.find((a) => a.key === 'slow_burn')).toBeUndefined();
@@ -597,7 +610,7 @@ describe('ReadingEvaluator', () => {
     it('awards monthly_reader_2 when 10+ books finished in current month', async () => {
       repo.countBooksFinishedInMonth.mockResolvedValue(10);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards).toContainEqual(expect.objectContaining({ key: 'monthly_reader_2' }));
@@ -606,7 +619,7 @@ describe('ReadingEvaluator', () => {
     it('does not award monthly_reader_2 when fewer than 10 books', async () => {
       repo.countBooksFinishedInMonth.mockResolvedValue(9);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(),
       );
       expect(awards.find((a) => a.key === 'monthly_reader_2')).toBeUndefined();
@@ -615,7 +628,7 @@ describe('ReadingEvaluator', () => {
     it('does not award monthly_reader_2 when already earned', async () => {
       repo.countBooksFinishedInMonth.mockResolvedValue(15);
       const awards = await evaluator.evaluate(
-        { userId: 1, isSuperuser: false, eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
+        { userId: 1, isSuperuser: false, timeZone: 'UTC', eventName: ACHIEVEMENT_EVENT_BOOK_STATUS_CHANGED, payload: makeStatusPayload() as never },
         new Set(['monthly_reader_2']),
       );
       expect(awards.find((a) => a.key === 'monthly_reader_2')).toBeUndefined();
diff --git a/server/src/modules/achievement/evaluators/reading.evaluator.ts b/server/src/modules/achievement/evaluators/reading.evaluator.ts
index c334019b5..3a980047c 100644
--- a/server/src/modules/achievement/evaluators/reading.evaluator.ts
+++ b/server/src/modules/achievement/evaluators/reading.evaluator.ts
@@ -87,7 +87,7 @@ export class ReadingEvaluator implements IAchievementEvaluator {
       this.evaluateEarlyBird(payload, earnedKeys, awards);
       this.evaluateOneSitting(payload, earnedKeys, awards);
       await this.evaluatePowerHour(payload, earnedKeys, awards);
-      await this.evaluateSpeedReader(ctx.userId, payload, earnedKeys, awards);
+      await this.evaluateSpeedReader(ctx.userId, ctx.timeZone, payload, earnedKeys, awards);
     }
 
     if (ctx.eventName === ACHIEVEMENT_EVENT_BACKFILL) {
@@ -104,7 +104,7 @@ export class ReadingEvaluator implements IAchievementEvaluator {
       await this.evaluateMonthlyReader2Backfill(ctx.userId, earnedKeys, awards);
       await this.evaluateOneSittingBackfill(ctx.userId, earnedKeys, awards);
       await this.evaluatePowerHourBackfill(ctx.userId, earnedKeys, awards);
-      await this.evaluateSpeedReaderBackfill(ctx.userId, earnedKeys, awards);
+      await this.evaluateSpeedReaderBackfill(ctx.userId, ctx.timeZone, earnedKeys, awards);
     }
 
     return awards;
@@ -338,12 +338,13 @@ export class ReadingEvaluator implements IAchievementEvaluator {
 
   private async evaluateSpeedReader(
     userId: number,
+    timeZone: string,
     payload: ReadingSessionSavedPayload,
     earnedKeys: Set<string>,
     awards: AchievementAward[],
   ): Promise<void> {
     if (earnedKeys.has('speed_reader')) return;
-    const pages = await this.repo.getPagesOnDay(userId, payload.startedAt);
+    const pages = await this.repo.getPagesOnDay(userId, payload.startedAt, timeZone);
     if (pages >= SPEED_READER_PAGES) {
       awards.push({ key: 'speed_reader', context: { pages } });
     }
@@ -357,9 +358,9 @@ export class ReadingEvaluator implements IAchievementEvaluator {
     }
   }
 
-  private async evaluateSpeedReaderBackfill(userId: number, earnedKeys: Set<string>, awards: AchievementAward[]): Promise<void> {
+  private async evaluateSpeedReaderBackfill(userId: number, timeZone: string, earnedKeys: Set<string>, awards: AchievementAward[]): Promise<void> {
     if (earnedKeys.has('speed_reader')) return;
-    const maxDayPages = await this.repo.getMaxPagesInADay(userId);
+    const maxDayPages = await this.repo.getMaxPagesInADay(userId, timeZone);
     if (maxDayPages >= SPEED_READER_PAGES) {
       awards.push({ key: 'speed_reader', context: { pages: maxDayPages } });
     }
diff --git a/server/src/modules/library/library-scan-scheduler.service.ts b/server/src/modules/library/library-scan-scheduler.service.ts
index 5bca26cfa..0194173b8 100644
--- a/server/src/modules/library/library-scan-scheduler.service.ts
+++ b/server/src/modules/library/library-scan-scheduler.service.ts
@@ -70,6 +70,7 @@ export class LibraryScanSchedulerService implements OnApplicationBootstrap, OnMo
 
       const job = CronJob.from({
         cronTime: expression,
+        timeZone: this.timeZone,
         onTick: () => this.runScheduledScan(libraryId),
         start: false,
       });
diff --git a/server/src/modules/reading-session/reading-session.service.ts b/server/src/modules/reading-session/reading-session.service.ts
index ca256a88b..4c0ad4571 100644
--- a/server/src/modules/reading-session/reading-session.service.ts
+++ b/server/src/modules/reading-session/reading-session.service.ts
@@ -86,7 +86,7 @@ export class ReadingSessionService {
           endedAt,
           progressDelta: dto.progressDelta ?? null,
           endProgress: dto.endProgress ?? null,
-          timezone: (user.settings as unknown as UserSettings)?.timezone ?? 'UTC',
+          timezone: resolveTimeZone((user.settings as unknown as UserSettings)?.timezone, 'UTC'),
         });
       }
     } catch (error) {