Cron expression parser
Explain a cron expression in plain English and show the next run times.
How it works
Translates a cron expression into a sentence and lists the next several times it will fire.
The field order is minute, hour, day of month, month, day of week — and the two day fields are the trap. When both are restricted, most cron implementations treat them as OR rather than AND, so `0 0 1 * 1` fires on the 1st of the month *and* every Monday, not on Mondays that fall on the 1st. That behaviour surprises almost everyone the first time.
Step values like */15 mean every fifteenth unit from the start of the range, not every fifteen minutes from now. `*/15` in the minute field fires at :00, :15, :30 and :45 regardless of when the job was created.
Cron runs in the server’s timezone unless configured otherwise, which is the usual cause of jobs firing an hour out twice a year. Schedules near the daylight-saving transition can be skipped or repeated.
This tool runs entirely in your browser. Nothing you enter is sent to a server, logged or stored, and the page keeps working with the network disconnected.
Common questions
- What is the order of cron fields?
- Minute, hour, day of month, month, day of week. Some systems add a seconds field at the front or a year field at the end.
- Why does my job run on the wrong days?
- Almost certainly the day-of-month and day-of-week fields. When both are restricted, most implementations OR them rather than AND them.
- What does */15 mean?
- Every fifteenth unit from the start of the range — :00, :15, :30, :45 — not fifteen minutes from when the job was created.
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Sources
- Calculated on this page — At One Place