Cron Jobs and Daylight Saving: Skipped and Double Runs
What happens to jobs at 1:30 and 2:30 when clocks change, and how to avoid it.
By the TurantTools Dev team · Updated October 27, 2026 · 2 min read
A cron job set for 2:30 AM in a zone with daylight saving can be skipped one night a year and, with some schedulers, run twice another night. The clock jumps from 2:00 to 3:00 in spring, and repeats 1:00–2:00 in autumn.
| Schedule | Spring forward | Fall back |
|---|---|---|
| 30 2 * * * | No 2:30 that night: may be skipped or run at 3:00, depending on the cron daemon | Runs once |
| 30 1 * * * | Runs once | 1:30 happens twice: may run twice |
| 30 4 * * * | Runs once | Runs once |
Avoiding it
- Run servers and schedulers in UTC, which has no daylight saving.
- If jobs must follow local time, schedule them outside 1:00–3:00.
- Make jobs idempotent, so a second run in the same window does no harm.