About this tool
Daylight saving time (DST) shifts a region's clocks forward in the spring and back in the autumn, lengthening evening daylight during summer months. About 70 countries observe some form of DST, but rules vary widely — start and end dates, the size of the shift, and even whether DST exists at all are determined by local law.
This tool tells you, for any timezone you select, whether DST is currently active, when this year's start and end transitions occur, and the standard versus DST offsets. It is essential for confirming meeting times across the "spring forward" and "fall back" weekends, when scheduling errors are most common.
How to use it
- 1Search and select any city or IANA timezone.
- 2Read the headline: DST is either currently active, currently inactive, or not observed at all in that region.
- 3Check the transition dates to know when the next clock change happens.
- 4Compare standard and DST offsets to plan around the one-hour shift.
Common use cases
- Confirming whether a recurring international meeting needs to be rescheduled after DST
- Verifying transit and flight times around DST weekends
- Travel planning — knowing whether to expect a clock change at your destination
- Software developers handling datetime arithmetic across DST boundaries
- Confirming exchange or market hours during transition weekends
How it works
The tool samples UTC offsets for the timezone month by month across the year. If the offset changes, the zone observes DST.
A binary search then narrows down the exact transition date and time within the month where the change occurs.
Frequently asked questions
Which countries observe DST?
Most of Europe, North America, parts of South America and Oceania. Most of Asia and Africa do not. The list changes — some countries (Russia, Turkey) have abolished DST in recent years.
When does DST start and end in the US and Europe?
US DST runs from the second Sunday in March to the first Sunday in November. EU DST runs from the last Sunday in March to the last Sunday in October. The two regions are not perfectly aligned, so trans-Atlantic meetings can drift for about three weeks each year.
Why does the offset change between summer and winter?
During DST the local clock is set one hour ahead of standard time, so the offset from UTC is one hour greater. Example: New York is UTC-5 in winter (EST) and UTC-4 in summer (EDT).
Is DST being abolished?
It is debated in many regions. The EU voted to abolish mandatory DST in 2019 but implementation has been postponed. In the US, the Sunshine Protection Act has passed the Senate but stalled in the House. As of now, the rules remain in effect.