Time Zone Converter
Convert a time from one zone to another, and find the window where two working days actually overlap.
Formula
Target time = source time + (target UTC offset − source UTC offset)
- Offsets shift with daylight saving, on different dates in each country
- UK clocks are UTC in winter and UTC+1 in summer
London 14:00 GMT is 09:00 in New York, which is UTC−5
How Offsets Work
Zones are expressed as offsets from UTC, Coordinated Universal Time. To convert, subtract the source offset and add the destination one.
14:00 in New York (UTC−5) is 19:00 UTC, which is 20:00 in Paris (UTC+1).
Note that GMT and UTC are not interchangeable in practice: the UK uses GMT in winter and British Summer Time (UTC+1) in summer, so "GMT" on a UK invitation is wrong for half the year.
Daylight Saving Breaks the Arithmetic
Offsets are not fixed. Worse, countries change clocks on different dates: the EU and UK switch on the last Sunday in March, the US on the second Sunday in March.
For two or three weeks each spring and autumn, the usual gap between London and New York changes by an hour. Meetings scheduled months ahead across that window routinely land wrong.
Much of the southern hemisphere shifts in the opposite direction, and many countries near the equator do not observe it at all.
Finding a Workable Window
Overlap shrinks fast with distance. London and New York share a comfortable afternoon; London and Sydney have almost no overlap in normal hours, which is why one side always takes an early or late call.
A few practical habits help: quote times with the zone attached, use UTC for anything technical, and remember that some zones are offset by 30 or 45 minutes — India is UTC+5:30 and Nepal UTC+5:45.
Quick Reference
| City | Standard offset | At 12:00 London |
|---|---|---|
| Los Angeles | UTC−8 | 04:00 |
| New York | UTC−5 | 07:00 |
| London | UTC+0 | 12:00 |
| Berlin | UTC+1 | 13:00 |
| Dubai | UTC+4 | 16:00 |
| Tokyo | UTC+9 | 21:00 |
| Sydney | UTC+10 | 22:00 |
Frequently Asked Questions
- How do I convert between time zones?
- Convert to UTC by subtracting the source offset, then add the destination offset. 14:00 in New York is 19:00 UTC and 20:00 in Paris.
- Is GMT the same as UTC?
- Not in practice. UTC is fixed, while the UK uses GMT in winter and British Summer Time in summer, so a UK time labelled GMT is wrong for half the year.
- Why do time differences change during the year?
- Countries start and end daylight saving on different dates, so the gap between two cities can shift by an hour for a few weeks each spring and autumn.
- Are all time zones whole hours?
- No. India is UTC+5:30 and Nepal UTC+5:45, among others, so assuming whole-hour offsets produces errors.