# Bun Set a time zone in Bun

> Set a time zone in Bun

- Skill: `jarle/bun-set-a-time-zone-in-bun` (Agent Skill)
- Install (CLI): `npx skillmds@latest add jarle/bun-set-a-time-zone-in-bun`
- Raw SKILL.md: https://api.skillmd.com/api/skills/jarle/bun-set-a-time-zone-in-bun/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: jarle (https://skillmd.com/u/jarle)
- Updated: 2026-09-21
- Page: https://skillmd.com/skills/jarle/bun-set-a-time-zone-in-bun

---


# Set a time zone in Bun

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="https://mintcdn.com/bun-1dd33a4e/nIz6GtMH5K-dfXeV/icons/typescript.svg?fit=max&auto=format&n=nIz6GtMH5K-dfXeV&q=85&s=5d73d76daf7eb7b158469d8c30d349b0" theme={"theme":{"light":"github-light","dark":"dracula"}}
process.env.TZ = "America/New_York";
```

***

Alternatively, this can be set from the command line when running a Bun command.

```sh terminal icon="terminal" theme={"theme":{"light":"github-light","dark":"dracula"}}
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="https://mintcdn.com/bun-1dd33a4e/nIz6GtMH5K-dfXeV/icons/typescript.svg?fit=max&auto=format&n=nIz6GtMH5K-dfXeV&q=85&s=5d73d76daf7eb7b158469d8c30d349b0" theme={"theme":{"light":"github-light","dark":"dracula"}}
new Date().getHours(); // => 18

process.env.TZ = "America/New_York";

new Date().getHours(); // => 21
```