CalcWhenTime Zone Converter
9:00 AM in New York is 2:00 PM in London on a November day — a 5-hour difference, with both cities on standard time.
How it works
Enter a time in one zone and read it instantly in another — the call time, the kickoff, the deadline — with the difference in hours printed so you can sanity-check it. The conversion is done for today's date using the full official zone rules, so daylight-saving weeks, when the usual gap grows or shrinks by an hour, come out right.
That last point is where memory fails people: New York to London is usually 5 hours, but for a few weeks each spring and autumn it is 4. This tool never relies on the usual — it asks the zone database every time.
The method
The entered wall time is resolved in the from-zone using the IANA time zone database (through the browser's Intl engine): the zone offset is computed iteratively so the exact UTC instant is found, then that instant is rendered in the to-zone. Offsets shown are the zones' UTC offsets on today's date.
Frequently asked questions
Why is the difference sometimes an hour off from what I remember?
Daylight saving starts and ends on different dates in different countries. For a few weeks a year, familiar gaps like New York–London are 4 hours instead of 5. The converter always uses today's real offsets.
Can I convert a time on a future date?
The conversion uses today's date, which is where almost all meeting-planning happens. Offsets for far-future dates can differ if a country changes its rules, which happens more often than you would think.
What does UTC mean in the list?
Coordinated Universal Time — the world's reference clock, with no daylight saving ever. Aviation, servers and science schedule in it.