Time zone converter
Plan a meeting time across multiple places: enter its date and local time in the first zone, then see that same instant in every selected zone.
The first zone sets the entered date and local time.
Choose a zone, or use your browser’s local date, time and zone.
Included
- An automatic starter scenario using the browser’s current local date, time and zone
- Two to eight ordered named IANA zones
- The first zone defines the entered local date and time
- Explicit choice when a local time occurs twice
- Clear rejection when a local time does not exist
Not included
- Live clocks or a continuously changing ‘now’
- Fixed-offset and abbreviation input such as CST
- Calendar invitations, working hours and meeting availability
- Guarantees that future legal time-zone rules will not change
What this means
A local clock reading is not always one instant. During an autumn clock change the same reading can occur twice; during a spring clock change some readings do not occur at all. This calculator identifies both cases instead of silently choosing.
Once the date and time in the first zone, plus any overlap choice, resolve to one exact instant, every selected row formats that same instant in its named zone. This is why all rows remain synchronized even when dates or offsets differ.
Named-zone rules come from the browser’s maintained IANA data. Governments can change future rules, so a future conversion is a planning result based on the data available in your browser today.
Formula & worked example
local date + local time + first named zone → exact instant exact instant + each selected named zone → local date, local time and UTC offset
Convert 27 October 2024 at 02:30 in Europe/Berlin
- Earlier occurrence
- 02:30 at UTC+02:00
- Later occurrence
- 02:30 at UTC+01:00
- Required action
- Choose which occurrence is intended
The calculator converts only after the overlap choice identifies one exact instant.
How this calculation works
The calculation follows the formulas, definitions and assumptions explained on this page. The references below support the method and any stated boundaries.
Official sources
- IANA Time Zone Database — Named-zone rules, offsets and daylight-saving changes
- ECMAScript Temporal — Zoned date-time disambiguation and same-instant conversion