Blog / Time zones
DST gaps, folds, and time zone conversion
How Long Until editorial · 2026-07-21
Spring-forward removes an hour; fall-back repeats one. Converters should use IANA zones, not a handwritten UTC offset.
“EST” is not a time zone database entry you can trust year-round. New York observes daylight saving; a fixed −5 offset is wrong for half the year.
The time zone converter takes IANA names such as America/New_York and asks the browser for the offset at that instant. Spring-forward creates a gap (2:30 a.m. may not exist). Fall-back creates a fold (1:30 a.m. happens twice).
If you schedule a meeting, pick a zone and a date, then convert. Do not add “plus six hours” in your head across a DST boundary. The hours from now tool adds milliseconds to Date.now(), which is the safer pattern for durations.