Daylight saving time checker
Check whether a date falls in daylight saving time for any time zone, with its UTC offset, time zone abbreviation and the exact moments the clocks change.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Query
Offsets are computed live with the browser Intl API, no external time zone database; a date is in DST when its offset is larger than the smallest offset of that year.
Result
Pick a date and a time zone to see whether daylight saving time applies.
What this tool does
- Before booking a call across time zones, check whether the other side is on daylight saving time so you do not land in the hour the clocks just moved.
- Turn abbreviations such as EDT/EST or BST/GMT into a real UTC offset when you need to know what “10:00” in an email actually means.
- Debug logs and incident timelines: confirm whether a date was in DST or standard time before converting local timestamps to UTC.
- Look up the exact date and moment of the next clock change before travelling, so you know which day loses or gains an hour.
Example
Input
Time zone America/New_York, date 2026-07-01 12:00
Output
Local 2026-07-01 12:00 (Wednesday), UTC offset UTC-04:00, abbreviation EDT, daylight saving time; standard offset UTC-05:00 and DST offset UTC-04:00; clock changes that year: 2026-03-08T07:00Z (UTC-05:00 → UTC-04:00, forward) and 2026-11-01T06:00Z (UTC-04:00 → UTC-05:00, back)
Change the date to 2026-01-15 12:00 and you get UTC-05:00, EST and standard time — the same zone has a different offset in winter.
Frequently asked questions
How does it decide whether daylight saving time applies?
It computes the real UTC offset at the queried instant and then scans the offsets used by that zone during the year, taking the smallest one as standard time. A larger offset means DST; if both are equal the zone has no daylight saving time at all, as with Asia/Shanghai (UTC+08:00 all year).
Why do most Asian zones report “no daylight saving time”?
Mainland China, Hong Kong, Taipei, Tokyo, Seoul, Singapore and Bangkok do not observe DST today, so their offset never changes. A few Asian zones such as Iran and Israel still do, and selecting them shows two clock changes per year.
Why is the southern hemisphere the other way round?
Because summer there runs from December to February. Sydney, for example, is UTC+11:00 in January (DST) and UTC+10:00 in July (standard), with the changes happening in April and October — the mirror image of New York or London.
Does it need a network connection or a time zone database download?
No. Every offset is computed live by the Intl.DateTimeFormat API built into the browser (or Node), so the tool works fully offline and never uploads the date you query.
Why are clock changes reported to the minute?
The tool first scans day by day to find which day changed, then bisects down to the minute. Real transitions always happen on a whole minute (usually a whole hour, half an hour on Lord Howe Island), so minute precision is enough to show the exact moment.
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