Timezone Offset Calculator
Get the UTC/GMT offset for a selected instant in one of the provided IANA time zones.
How to use
- Enter a device-local date and time.
- Choose a time zone from the list.
- Calculate to see that instant's GMT offset.
Capabilities and scope
Check the offset for the same instant in zones such as Seoul, Tokyo, London, and New York.
How it works
The input instant becomes a JavaScript `Date`, then `Intl.DateTimeFormat` formats the selected zone with `timeZoneName: longOffset`. Daylight-saving rules are therefore reflected where the runtime's time-zone data supports them.
Example
`America/New_York` can display GMT-05:00 or GMT-04:00 depending on the date.
Useful for
- Check a zone's offset on a particular date
- Inspect DST offset changes
- Verify time-zone assumptions for logs or meetings
Before you use it
- The UI is limited to the 12 IANA zones provided in its selection list.
- The input `datetime-local` value is first interpreted in the current device's local zone.
Standards and references
Frequently asked questions
Can New York's offset change by season?
Yes. `Intl` can apply the zone's daylight-saving rule for the selected date.
Can I type any IANA zone?
No. The current UI uses a predefined zone list.