diff --git a/packages/api/src/agents/__tests__/initialize.test.ts b/packages/api/src/agents/__tests__/initialize.test.ts
index 1bec88f837..e770dbd630 100644
--- a/packages/api/src/agents/__tests__/initialize.test.ts
+++ b/packages/api/src/agents/__tests__/initialize.test.ts
@@ -664,6 +664,31 @@ describe('initializeAgent — stable and dynamic instruction fields', () => {
     expect(result.additional_instructions).toBe('Conversation opened at 2023-12-31T23:59:58.000Z');
   });
 
+  it('resolves temporal special vars in the request timezone', async () => {
+    const { agent, req, res, loadTools, db } = createMocks();
+    agent.instructions = 'It is currently {{current_datetime}}.';
+    req.conversationCreatedAt = '2024-01-15T18:30:00.000Z';
+    req.body = { timezone: 'America/New_York' };
+
+    const result = await initializeAgent(
+      {
+        req,
+        res,
+        agent,
+        loadTools,
+        endpointOption: { endpoint: EModelEndpoint.agents },
+        allowedProviders: new Set([Providers.OPENAI]),
+        isInitialAgent: true,
+      },
+      db,
+    );
+
+    expect(result.instructions).toBeUndefined();
+    expect(result.additional_instructions).toBe(
+      'It is currently 2024-01-15 13:30:00 -05:00 (Monday).',
+    );
+  });
+
   it('keeps non-temporal special vars in stable instructions', async () => {
     const { agent, req, res, loadTools, db } = createMocks();
     agent.instructions = 'You are helping {{current_user}}.';
diff --git a/packages/api/src/agents/initialize.ts b/packages/api/src/agents/initialize.ts
index b3a3205c00..ebbc6be73c 100644
--- a/packages/api/src/agents/initialize.ts
+++ b/packages/api/src/agents/initialize.ts
@@ -1112,6 +1112,7 @@ export async function initializeAgent(
       text: agent.instructions,
       user: req.user ? (req.user as unknown as TUser) : null,
       now: req.conversationCreatedAt,
+      timezone: req.body?.timezone,
     });
     if (hasTemporalSpecialVars(agent.instructions)) {
       agent.instructions = undefined;
diff --git a/packages/api/src/types/http.ts b/packages/api/src/types/http.ts
index 219b2729f7..b3a34df383 100644
--- a/packages/api/src/types/http.ts
+++ b/packages/api/src/types/http.ts
@@ -16,6 +16,8 @@ export type RequestBody = {
   model?: string;
   key?: string;
   endpointOption?: Partial<TEndpointOption>;
+  /** Browser IANA timezone used to resolve local-time prompt variables (e.g. `{{current_datetime}}`). */
+  timezone?: string;
 };
 
 export type ServerRequest = Request<unknown, unknown, RequestBody> & {
diff --git a/packages/data-provider/specs/parsers.timezone.spec.ts b/packages/data-provider/specs/parsers.timezone.spec.ts
new file mode 100644
index 0000000000..cd8583b95a
--- /dev/null
+++ b/packages/data-provider/specs/parsers.timezone.spec.ts
@@ -0,0 +1,66 @@
+import { replaceSpecialVars } from '../src/parsers';
+
+/**
+ * Exercises real `dayjs` timezone conversion (no module mock) so the assertions
+ * hold regardless of the machine's local timezone — the anchor instant and the
+ * requested zone are both fixed.
+ */
+describe('replaceSpecialVars timezone handling', () => {
+  const anchor = '2024-01-15T18:30:00.000Z';
+
+  test('resolves {{current_datetime}} in the supplied timezone', () => {
+    const result = replaceSpecialVars({
+      text: '{{current_datetime}}',
+      now: anchor,
+      timezone: 'America/New_York',
+    });
+    expect(result).toBe('2024-01-15 13:30:00 -05:00 (Monday)');
+  });
+
+  test('resolves {{current_date}} across a day boundary into the local zone', () => {
+    const result = replaceSpecialVars({
+      text: '{{current_date}}',
+      now: '2024-01-15T02:30:00.000Z',
+      timezone: 'America/New_York',
+    });
+    expect(result).toBe('2024-01-14 (Sunday)');
+  });
+
+  test('shifts the local day forward for zones ahead of UTC', () => {
+    const result = replaceSpecialVars({
+      text: '{{current_date}} | {{current_datetime}}',
+      now: anchor,
+      timezone: 'Asia/Tokyo',
+    });
+    expect(result).toBe('2024-01-16 (Tuesday) | 2024-01-16 03:30:00 +09:00 (Tuesday)');
+  });
+
+  test('keeps {{iso_datetime}} in UTC regardless of timezone', () => {
+    const result = replaceSpecialVars({
+      text: '{{iso_datetime}}',
+      now: anchor,
+      timezone: 'Asia/Tokyo',
+    });
+    expect(result).toBe('2024-01-15T18:30:00.000Z');
+  });
+
+  test('falls back to the un-zoned anchor when the timezone is invalid', () => {
+    const withInvalid = replaceSpecialVars({
+      text: '{{current_datetime}}',
+      now: anchor,
+      timezone: 'Not/AZone',
+    });
+    const withNone = replaceSpecialVars({ text: '{{current_datetime}}', now: anchor });
+    expect(withInvalid).toBe(withNone);
+  });
+
+  test('ignores an empty timezone string', () => {
+    const withEmpty = replaceSpecialVars({
+      text: '{{current_datetime}}',
+      now: anchor,
+      timezone: '',
+    });
+    const withNone = replaceSpecialVars({ text: '{{current_datetime}}', now: anchor });
+    expect(withEmpty).toBe(withNone);
+  });
+});
diff --git a/packages/data-provider/src/createPayload.ts b/packages/data-provider/src/createPayload.ts
index 783ad7f9dd..da20e7d1ac 100644
--- a/packages/data-provider/src/createPayload.ts
+++ b/packages/data-provider/src/createPayload.ts
@@ -2,6 +2,15 @@ import type * as t from './types';
 import { EndpointURLs } from './config';
 import * as s from './schemas';
 
+/** Resolves the browser's IANA timezone so the server can localize prompt variables. */
+function getUserTimezone(): string | undefined {
+  try {
+    return Intl.DateTimeFormat().resolvedOptions().timeZone || undefined;
+  } catch {
+    return undefined;
+  }
+}
+
 export default function createPayload(submission: t.TSubmission) {
   const {
     isEdited,
@@ -42,6 +51,7 @@ export default function createPayload(submission: t.TSubmission) {
     isContinued: !!(isEdited && isContinued),
     ephemeralAgent: s.isAssistantsEndpoint(endpoint) ? undefined : ephemeralAgent,
     manualSkills: s.isAssistantsEndpoint(endpoint) ? undefined : manualSkills,
+    timezone: getUserTimezone(),
   };
 
   return { server, payload };
diff --git a/packages/data-provider/src/parsers.ts b/packages/data-provider/src/parsers.ts
index 684b233e48..d34d068cbc 100644
--- a/packages/data-provider/src/parsers.ts
+++ b/packages/data-provider/src/parsers.ts
@@ -1,9 +1,10 @@
 import dayjs from 'dayjs';
+import utc from 'dayjs/plugin/utc';
+import timezonePlugin from 'dayjs/plugin/timezone';
 import type { ZodIssue } from 'zod';
 import type * as a from './types/assistants';
 import type * as s from './schemas';
 import type * as t from './types';
-import { ContentTypes } from './types/runs';
 import {
   openAISchema,
   openRouterSchema,
@@ -18,8 +19,12 @@ import {
   compactAssistantSchema,
 } from './schemas';
 import { bedrockInputSchema } from './bedrock';
+import { ContentTypes } from './types/runs';
 import { alternateName } from './config';
 
+dayjs.extend(utc);
+dayjs.extend(timezonePlugin);
+
 type EndpointSchema =
   | typeof openAISchema
   | typeof openRouterSchema
@@ -424,21 +429,40 @@ export function findLastSeparatorIndex(text: string, separators = SEPARATORS): n
   return lastIndex;
 }
 
+/**
+ * Anchors a dayjs instant to the user's IANA timezone when one is supplied,
+ * so local-time special vars reflect the user's wall clock rather than the
+ * server's. Falls back to the original instant for missing or invalid zones.
+ */
+function applyTimezone(value: dayjs.Dayjs, timezone?: string): dayjs.Dayjs {
+  if (!timezone) {
+    return value;
+  }
+  try {
+    const zoned = value.tz(timezone);
+    return zoned.isValid() ? zoned : value;
+  } catch {
+    return value;
+  }
+}
+
 export function replaceSpecialVars({
   text,
   user,
   now: inputNow,
+  timezone,
 }: {
   text: string;
   user?: t.TUser | null;
   now?: string | number | Date;
+  timezone?: string;
 }) {
   let result = text;
   if (!result) {
     return result;
   }
 
-  const now = inputNow != null ? dayjs(inputNow) : dayjs();
+  const now = applyTimezone(inputNow != null ? dayjs(inputNow) : dayjs(), timezone);
   const weekdayName = now.format('dddd');
 
   const currentDate = now.format('YYYY-MM-DD');
diff --git a/packages/data-provider/src/types.ts b/packages/data-provider/src/types.ts
index 6eac428568..6a8db985e8 100644
--- a/packages/data-provider/src/types.ts
+++ b/packages/data-provider/src/types.ts
@@ -127,6 +127,8 @@ export type TPayload = Partial<TMessage> &
      * before the LLM turn runs.
      */
     manualSkills?: string[];
+    /** Browser IANA timezone (e.g. `America/New_York`) used to resolve local-time prompt variables server-side. */
+    timezone?: string;
   };
 
 export type TEditedContent =