Skip to main content

Set the time zone

Edit on Github

Date, Intl, and Temporal all format times in the process time zone, which defaults to the operating system setting. The TZ environment variable overrides it, which makes time-dependent behavior reproducible.

The current time zone is visible through the Intl API.
const zone = Intl.DateTimeFormat().resolvedOptions().timeZone;
console.log(zone); // Europe/Warsaw (or whatever the OS is set to)
Everything that formats local time follows it.
console.log(new Date().toString());
Start the process with TZ set to pin the zone, for example to keep timestamps in CI logs consistent or to reproduce a user's bug report: TZ=Asia/Tokyo deno run main.ts Asia/Tokyo Thu Jun 11 2026 22:15:00 GMT+0900 (Japan Standard Time) TZ=UTC deno run main.ts UTC
The Temporal API is the preferred way to work with zoned time. The current moment in the process zone keeps its zone name attached.
const now = Temporal.Now.zonedDateTimeISO();
console.log(now.timeZoneId); // Europe/Warsaw (follows TZ like the above)
Getting the same moment in another zone is an argument, not a process setting, so zone conversions stay explicit and local to the call.
const tokyoTime = Temporal.Now.zonedDateTimeISO("Asia/Tokyo");
console.log(tokyoTime.hour); // e.g. 22
The Intl API formats a value for another zone the same way.
const tokyo = new Intl.DateTimeFormat("en-US", {
  timeStyle: "long",
  timeZone: "Asia/Tokyo",
}).format(new Date());
console.log(tokyo);

Run this example locally using the Deno CLI:

deno run https://docs.deno.com/examples/scripts/set_timezone.ts

Additional resources

Did you find what you needed?

Privacy policy