Timezone converter
Convert between IANA time zones with date, DST, and UTC.
Results
Enter data and click Calculate.
How to use this calculator
- Pick a date and time, plus source and target zones. Optionally add up to 4 extra zones.
- Offset and daylight saving (DST) are computed for the date you chose — the result is the same instant: source local, target local, and UTC.
- City-pair presets only fill fields; click Calculate for results.
Offsets and UTC
Every IANA zone (e.g. America/New_York) has an offset from UTC (-05:00 or -04:00 in summer) — a clock shift, not a separate "speed" of time. UTC is the reference point with no shift and no daylight saving, so the calculator always shows the same instant in UTC too.
Daylight saving time (DST)
- Many zones change their offset twice a year (e.g. US: second Sunday of March and first Sunday of November) — this changes the hour difference versus zones without DST (e.g. UTC, most of Asia).
- Some city pairs have an hour difference that itself changes during the year, because only one side observes DST (Europe and the US switch on different dates).
- This calculator computes the offset for the specific date you pick — not "right now" — so the result is correct for future dates too.
Worked example: a meeting across a DST change
The same local clock time in Warsaw the week before and after Europe’s spring-forward maps to a different New York time, because the US and Europe change clocks on different dates.
| Date (Warsaw) | Source | Target (New York) | Note |
|---|---|---|---|
| 2026-03-22 15:00 | Europe/Warsaw (UTC+1) | ~10:00 America/New_York (UTC−4) | Europe still winter; US already on DST |
| 2026-03-29 15:00 | Europe/Warsaw (UTC+2) | ~09:00 America/New_York (UTC−4) | After Europe’s spring-forward — 1 hour shift vs the prior week |
Try both dates in the calculator — your browser’s Intl engine supplies the offsets.
Offsets: winter vs summer (ballpark)
| Pair | Winter | Summer |
|---|---|---|
| Warsaw → New York | ~6 h | ~6 h (change dates differ!) |
| London → Tokyo | ~9 h | ~8 h |
| UTC → Los Angeles | ~8 h | ~7 h |
Around DST transition weeks the gap can temporarily differ — always compute for a concrete date.
Meeting-scheduling pitfalls
- "3pm my time" doesn’t mean the same hour for the other person — always state the zone or share a converter link.
- The week of a DST transition is confusing because the hour difference between zones temporarily shifts.
- Calendar apps handle recurring UTC-based meetings well, but can "drift" a meeting by an hour if it was saved in local time without a zone.
Why you should store UTC
In databases and logs, store time in UTC and convert to local time only in the presentation layer (UI). This removes DST ambiguity and lets you correctly compare and sort events from different zones without extra logic.
Examples
- 12:00 in Warsaw (summer, UTC+2) = 06:00 in New York (UTC-4) = 10:00 UTC.
- 09:00 in London (winter, UTC+0) = 18:00 in Tokyo (UTC+9) the same day.
- A meeting saved as "weekly at 10:00 local time" can land on a different UTC hour after a DST change in either zone.
FAQ — timezone conversion
- Does the calculator account for daylight saving time?
- Yes — the offset is computed for the selected date via the browser’s built-in Intl mechanism, so DST is always correct for that specific date.
- What does "Same instant (UTC)" mean?
- It’s the same point in time as your source and target, expressed with no zone shift — a reference point for comparison.
- Why does the hour difference between two zones sometimes change?
- Because one or both zones switch to daylight saving time on different dates — the gap can differ between winter and summer.
- Can I compare more than two zones at once?
- Yes — add up to 4 extra zones in the "Additional zones" fields, and the results table will show them all together.
- What happens when a meeting crosses a DST change between time zones?
- If only one side changes offset (or they change on different dates), the same local clock time on your side maps to a different clock time for the other party — check both dates in the calculator.
- Do the city-pair presets give a result right away?
- No — they only fill the source and target fields. Click Calculate to see the result.
- How do I know which zone represents my city?
- IANA zone names are based on one large city that represents the DST rule for a whole region, even if you live elsewhere in that country.
- What if the local time does not exist (DST spring-forward)?
- Some clock times are skipped when clocks jump forward — the calculator returns an error. Pick a local time that actually exists that day.