Time zone converter
A time zone converter shows one instant rendered in several places at once. Offsets are not fixed: most of Europe and North America shift by an hour twice a year, on different dates, so the gap between London and New York is five hours for most of the year and four for two short stretches in spring and autumn.
How to use it
The offsets and daylight-saving rules come from the browser’s own copy of the IANA time zone database rather than from a table stored here, which means they stay correct when a country changes its rules — and they do, several times a year. Zones that observe daylight saving are marked, because those are the ones where a meeting booked in March moves in October.
Questions
Because daylight saving starts and ends on different dates in different places. For two weeks in March, London and New York are four hours apart rather than five.