Cron expression explainer

Paste a cron schedule to read it in plain words, check each field, and see exactly when it will next run — in your time zone, in UTC or in the server’s.

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The five fields

* means every value; 1-5 a range; 1,15 a list; */15 every 15th value from the start.
Months and days of the week can be written as names: JAN–DEC and SUN–SAT. Sunday is 0 or 7.
@hourly, @daily, @weekly, @monthly and @yearly are shorthands for common schedules.

Which cron does this follow?

Standard five-field cron as in Vixie cron and cronie on Linux, Kubernetes CronJobs and GitHub Actions. Quartz, Spring and AWS EventBridge add a seconds or year field and characters such as ? and L, and are pointed out rather than misread.

What happens at daylight-saving changes?

A time skipped when clocks go forward does not occur that day, and a time repeated when they go back is shown once. Real cron daemons vary here, so scheduling important jobs outside 01:00–03:00 local time, or in UTC, avoids the question.

Why did my job run on an unexpected day?

If both day-of-month and day-of-week are set, cron runs when either matches: “0 0 13 * 5” is every 13th and every Friday, not only Friday the 13th.