Free Online Daylight Saving Time Checker and Clock Change Finder
Find the exact moment the clocks change in any time zone, in any year, with the offsets on either side and the hour that is skipped or repeated. The page also checks whether a particular date and time actually exists in that place, which is the question behind a surprising number of bugs.
Every date is worked out in your browser. Nothing you type is sent anywhere.
☀️ Which question?
Each change, with the offsets on either side.
| What happens | The exact moment there | Offsets, and what it means |
|---|
| Year | Clocks go forward | Clocks go back |
|---|
| When | What was worked out | Actions |
|---|
How dates are shown
The format only changes what you read. Every date you type into a date box is handled as year, month and day, so 02/09 can never be mistaken for the second of September in one place and the ninth of February in another.
Display
Full screen hides the page around the tool. Press Escape, or the button in the bar, to come back.
History
Your data
Settings, history and saved setups live in this browser and nowhere else. There is no account and no server, which also means clearing them here is final.
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How to Check When the Clocks Change
Two questions, one set of rules.
What to Know About Clock Changes
The missing hour, the repeated hour, and the bugs they cause.
Key Features & Capabilities
What it finds, and what it deliberately leaves to other pages.
About Daylight Saving Time
Daylight saving time moves the clock forward in spring and back in autumn so that the long evenings fall where people are awake. The idea is simple and the consequences are not, because moving a clock does not move time: it changes the relationship between a local time and the actual instant it names. Twice a year, for one hour, that relationship breaks down completely, and almost every awkward bug involving dates lives in those two hours.
Going forward is the cleaner of the two and the stranger. If the clocks jump from one in the morning to two, then every local time in that hour never occurs. A meeting at half past one on that date is not a time at all. Anything already stored at such a time has to be moved, and different pieces of software move it differently, which is how a single appointment ends up at two different instants in two different systems.
Going back is messier. The same local hour comes round a second time, so half past one names two instants roughly an hour apart. A log sorted by local time comes out in the wrong order, a job that runs at a fixed local time runs twice, and a daily total for that date covers twenty five hours. None of this announces itself: the figures are simply wrong once a year, in one direction, for one day.
The rules themselves are set country by country and change more often than people expect. Europe moves on the last Sunday of March and October, North America on the second Sunday of March and the first of November, the southern hemisphere runs the opposite way round, and a long list of countries have abandoned the practice, some of them recently. Rather than carry a table of rules that would quietly go out of date, this page reads the actual offsets out of the time zone data your own browser already holds, and finds the change by looking for the minute at which the offset moves.
Frequently Asked Questions
Dates, offsets and times that do not exist.