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Cron Expression Generator

Builds a valid cron expression from its own five fields — a shape of schedule, then a time, then a day — and writes the sentence that describes it from those same fields, so the expression and the explanation cannot disagree.

What this generator does

Produces a five-field cron expression, for testing schedule parsers and seeing worked examples of the syntax. Cron's field order is minute, hour, day of month, month, day of week.

How to use this tool

  1. Press generate for a cron expression example.

Worked examples

Format
*/15 3 * * 1 — every 15 minutes, in the 3am hour, on Mondays
Steps divide their unit
A minute step is always one of 2, 3, 4, 5, 6, 10, 12, 15, 20 or 30, and an hour step one of 2, 3, 4, 6, 8 or 12. A step of 7 would run at :00 through :56 and then wait four minutes, a gap once an hour that nobody asks for.

Common use cases

  • Learning cron syntax
  • Documentation examples
  • Placeholder scheduler configs

Limitations and good to know

  • A randomly generated schedule is unlikely to be one you actually want. Read what it means before pasting it into anything that will run.
  • Monthly and yearly schedules never land after the 28th, because a job set for the 31st does not run in February and that is a trap rather than an example. If you need month-end, cron alone cannot express it.
  • The five-field form here is the common denominator. Seconds fields, @reboot, @daily and the L, W and # characters exist in some schedulers and none of them appear here.

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