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Daylight saving time (DST) introduces predictable but easily missed edge cases in scheduling. This policy documents how DateAndTimePro.com handles them.
DST transitions
- On spring-forward dates, local clocks skip a period (often 02:00–03:00). Local times that fall in the skipped window do not exist; calculators surface a clear notice.
- On fall-back dates, local clocks repeat a period. Ambiguous local times default to the first occurrence and the alternate occurrence is shown for context.
- Conversions across zones with different DST schedules account for the rule in effect for each instant on each side of the conversion.
Jurisdictions without DST
- Many regions do not observe DST (for example, most of Asia, large parts of Africa, and several US territories and states).
- City hubs and time zone tools indicate whether a location currently observes DST.
Historical changes
DST rules have changed many times over the past century. We rely on the historical rules included in the public time zone database described in our Time Zone Information Policy.
Limitations of future predictions
Future DST behavior reflects current law. Several jurisdictions have proposed or partially adopted permanent standard or permanent daylight time but have not finalized implementation. Future-dated calculations should be treated as best estimates and verified before legal, travel, broadcast, or contractual reliance.
Published by Relationale LLC, founded by Keiron Brown. For questions about this document, see our Contact page or browse the Time Intelligence Trust Center.