What does this tool do
The Timezone Converter converts a date and time from one IANA timezone to one or more target timezones. Enter a wall-clock datetime in the source zone, and see the equivalent in each target zone. Supports all IANA timezones and correctly handles Daylight Saving Time. All conversion runs client-side via the browser Intl API.
How to use it
- Select source timezone — Choose the IANA timezone for your input time.
- Enter date and time — Type or pick the datetime in the source zone.
- Add target timezones — Select one or more target zones.
- View results — Each target shows the equivalent datetime and UTC offset.
- Change input — Edit the source datetime; all targets update.
How it works
All conversions derive from a single UTC millisecond value. The tool does not convert directly between two non-UTC timezones—it always goes through UTC. For wall-clock input in a given source zone, a two-pass DST-safe algorithm is used: first pass produces an approximate UTC instant; second pass corrects for DST fold or gap boundaries. Uses Intl.DateTimeFormat and the browser's timezone database.
All computation runs entirely in your browser. No data is sent to any server.
Use cases & examples
- Meetings — Convert meeting time for participants in different zones.
- Travel — Plan calls and events across timezones.
- Support — Communicate deadlines in the user's local time.
- Scheduling — Plan releases or events for a global audience.
- Learning — Understand DST and timezone offsets.
Example
- 2:00 PM in America/New_York (EST) → 8:00 PM in Europe/London (GMT), etc.
- DST transition: 2:30 AM may not exist in some zones; tool handles gaps.
Limitations & known constraints
- Browser timezone DB — Depends on the user's browser; outdated browsers may have wrong DST.
- IANA names — Abbreviations (e.g. PST) can be ambiguous; use full IANA IDs.
- DST boundaries — Fold/gap handling is correct for typical cases; edge cases may vary.
- No historical — Uses current DST rules; past rule changes may not be reflected.