EpochLab

DST Converter

Convert a time across a daylight-saving change

The two cases that break scheduling: a wall time that never existed, and one that happened twice. Both are detected and both instants are given.

Questions people ask

The things that come up about dst converters, answered plainly.

What happens to 02:30 when the clocks go forward?

It never happens. The clock jumps from 01:59:59 to 03:00:00, so any job or alarm set for 02:30 either does not run or runs at a substituted time, depending on the system. The page flags the gap explicitly.

What about the hour that happens twice?

In autumn, 01:30 occurs twice — once on summer time and once on standard. A bare local timestamp for it is genuinely ambiguous; the page gives both instants and their offsets so you can pick.

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