Time zone converter
Pick two zones and a time. Offsets come from the IANA time zone database — the same source operating systems use — so daylight saving is already applied and you never have to work out whether a region is currently on summer time.
Why the gap changes
An abbreviation is not a fixed offset. Many converters treat “EST” as permanently UTC−5. That is wrong for roughly eight months a year: the eastern United States switches to EDT (UTC−4) in March and back in November. The same applies to the UK (GMT→BST), Europe (CET→CEST) and Australia.
This page never stores a fixed number. Each zone maps to a real IANA zone and the offset is read at the moment you load the page, so it is correct whatever the season. Regions that do not observe daylight saving — India, Pakistan, Japan, Singapore, the Gulf — keep the same offset all year, which is why conversions to those places drift when your side changes and theirs does not.