Unit conversion
Time Zone Converter
Converts between time zones, where the rules change by legislation.
Result
Offsets come from your device's time zone database, so daylight saving transitions are applied for the specific date entered rather than today's offset.
See appointment bookingHow the calculation works
The offset between two zones applied to a time, accounting for whether either zone is observing daylight saving on the date in question. The offset is not a fixed property of a pair of places, since daylight saving transitions happen on different dates in different places and some places do not observe it at all.
What moves the number
- Whether either zone observes daylight saving on that date.
- Transition dates, which differ between regions.
- The specific date, not just the time.
- Legislative changes to zone rules.
Where this one goes wrong
The offset between two places changes several times a year and the transition dates do not align, which means there are periods of a few weeks each year when the usual difference between two cities is an hour out, and a meeting scheduled on the usual offset is wrong. Convert for the specific date. Zone rules also change by legislation with little notice, which is why systems carry a maintained time zone database rather than hard-coded offsets.
Before you quote
- Convert for the specific date, not just the time.
- Check whether either location observes daylight saving.
- Expect transition dates to differ between regions.
Questions
About this calculator
Why does the time difference between two cities change?
Because daylight saving transitions happen on different dates in different places, and some places do not observe it. There are periods each year when the usual difference is an hour out, which is when scheduled meetings go wrong.
Do I need the date to convert a time?
Yes, because the offset depends on whether either zone is observing daylight saving on that date. Converting a time without a date assumes an offset that is wrong for part of the year.
Why do time zone rules change?
Because they are set by legislation and governments change them, sometimes with little notice. That is why software uses a maintained time zone database rather than hard-coded offsets, and why a stale database produces wrong answers.
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How to use this calculator
- Date. Enter your own figure; the page starts at 2026-09-08.
- Time. Enter your own figure; the page starts at 09:00.
- From zone. Enter your own figure; the page starts at New York.
- To zone. Enter your own figure; the page starts at London.
The result updates as you type, so you can try a figure, see what it does to local time there, and change it back. Nothing you enter is sent anywhere or saved.
A worked example
These are the figures the calculator opens with. Every number in the results column below is produced by the same calculation the page runs, so you can follow it through before putting your own figures in.
What goes in
| Input | Value |
|---|---|
| Date | 2026-09-08 |
| Time | 09:00 |
| From zone | New York |
| To zone | London |
What comes out
| Result | Value |
|---|---|
| Local time there main result | 2026-09-08 14:00 |
| Time difference | +5h |
| Date change | Same day |
That time is 2026-09-08 14:00 in the destination zone, a difference of +5h (same day).
What each figure means
- Date
- A number, starting at 2026-09-08.
- Time
- A number, starting at 09:00.
- From zone
- Choose from Auckland, Sydney, Tokyo, Singapore, Dhaka, Mumbai / Kolkata, Dubai, Moscow, Berlin / Paris, London, UTC, São Paulo, New York, Chicago, Denver, Los Angeles, Honolulu.
- To zone
- Choose from Auckland, Sydney, Tokyo, Singapore, Dhaka, Mumbai / Kolkata, Dubai, Moscow, Berlin / Paris, London, UTC, São Paulo, New York, Chicago, Denver, Los Angeles, Honolulu.
What the results tell you
| Result | What it is |
|---|---|
| Local time there | The headline result. A category or planning selection, rather than a measured quantity. |
| Time difference | A category or planning selection, rather than a measured quantity. |
| Date change | A category or planning selection, rather than a measured quantity. |
Booking across time zones?
BDEVY builds booking systems that show customers only slots you can actually run, in their local time.