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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.
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.
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process.env.TZ = 'America/New_York';
Alternatively, this can be set from the command line when running a Bun command.
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.
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new Date().getHours(); // => 18

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

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