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Agents are time-aware out of the box: every session knows today’s date and the current time in the session’s timezone. You don’t reference a variable or add anything to your prompt — “tomorrow morning” and “next Tuesday” ground correctly from the first turn, on every channel (voice, text, and phone).

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What the agent knows

Fish Audio injects two pieces of world context server-side: The time is refreshed on every turn, so it stays accurate through long conversations and past midnight — it never freezes at the session’s start time.
Injection happens outside your configuration, so it never counts toward the system prompt’s character limit.

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Which timezone a session uses

The timezone is resolved once, when the session is created, taking the first that applies:
  1. timezone in the creation request — your explicit per-session choice, as an IANA name like Asia/Shanghai. An invalid name rejects the request with 422.
  2. The agent’s configured timezone — set on the agent in the Builder (Configuration → Timezone) or via the agent config API. Pin one when your agent serves a single region regardless of who calls.
  3. client_timezone — a hint with the end user’s browser timezone, sent automatically by the Web SDK in public-agent mode. Used only when neither of the above is set; an invalid hint is ignored rather than failing the session.
  4. The caller’s phone number — inbound calls infer the timezone from the caller’s country when that country has a single timezone.
  5. UTC otherwise.
In the browser, this means zero configuration: the SDK detects the visitor’s real timezone and the agent talks about “today” in the user’s local terms, not yours. With session token auth, the SDK’s automatic hint doesn’t apply — your backend creates the session, so set timezone (or forward the browser’s value as client_timezone) in the creation request:
API (curl)
Phone-number inference is country-level only. Countries that span several timezones (the US, Canada, Australia, Russia, Brazil) are skipped — set the agent’s timezone for those. Calls that resolve nothing run in UTC.

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Turn it off

Time awareness is on by default. To withhold both the date and the per-turn time from a session — for example a role-play agent set on a fictional date, or a test that must be reproducible — set world_context: false when creating the session:

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Going further

Authentication

All session-creation parameters, including timezone and world_context.

Dynamic variables

Personalize the rest of the prompt at session creation.