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bun.sh/docs/guides/runtime/timezone.mdx
2025-11-05 11:14:21 -08:00

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---
title: Set a time zone in Bun
sidebarTitle: Set time zone
mode: center
---
Bun supports programmatically setting a default time zone for the lifetime of the `bun` process. To do set, set the value of the `TZ` environment variable to a [valid timezone identifier](https://en.wikipedia.org/wiki/List_of_tz_database_time_zones).
<Note>
When running a file with `bun`, the timezone defaults to your system's configured local time zone.
When running tests with `bun test`, the timezone is set to `UTC` to make tests more deterministic.
</Note>
```ts process.ts icon="/icons/typescript.svg"
process.env.TZ = "America/New_York";
```
---
Alternatively, this can be set from the command line when running a Bun command.
```sh terminal icon="terminal"
TZ=America/New_York bun run dev
```
---
Once `TZ` is set, any `Date` instances will have that time zone. By default all dates use your system's configured time zone.
```ts process.ts icon="/icons/typescript.svg"
new Date().getHours(); // => 18
process.env.TZ = "America/New_York";
new Date().getHours(); // => 21
```