Cron Expression Explainer
Read any cron schedule in plain English and see exactly when it runs next.
| Field | Value | Means |
|---|
Both day fields are set, so cron runs on days that match either one, not only days matching both.
How to use the Cron Expression Explainer
- Type or paste a cron expression, or start from one of the examples.
- Read the plain-English summary and the meaning of each of the five fields.
- Check the next run times, in your own time zone or in UTC.
- Fix any field the tool flags, then copy the expression.
About this tool
Cron is the scheduler behind countless backups, reports and clean-up jobs on servers, and the same five-field format is used by CI pipelines, cloud schedulers and task runners. It is compact but easy to misread: a job meant for 9 in the morning on weekdays can just as easily run every minute of 9 o'clock, or on the 9th of every month.
This explainer translates the expression into a sentence, breaks it down field by field and lists the next times it will fire, so you can confirm it does what you expect before you deploy it. Errors are explained in plain words and the faulty field is highlighted, whether it is a value out of range, a backwards range or a sixth field copied from a system that counts seconds.
It also spells out cron's most surprising rule. When both the day-of-month and day-of-week fields are set, the job runs on days that match either one. "0 0 13 * 5" therefore runs on every Friday and on every 13th, not only on Friday the 13th.
Frequently asked questions
What do the five fields mean?
In order: minute (0 to 59), hour (0 to 23), day of the month (1 to 31), month (1 to 12 or JAN to DEC) and day of the week (0 to 7, where both 0 and 7 are Sunday, or SUN to SAT).
What does */15 mean?
A star means every value, and /15 takes every fifteenth one. In the minute field, */15 runs at minutes 0, 15, 30 and 45. 5/15 would start at minute 5 instead.
Why are my run times an hour off?
Cron uses the time zone of the machine it runs on, and servers usually use UTC. Switch the list to UTC to see what the server will do, and remember that daylight saving changes can skip or repeat local times.
Does it support seconds or Quartz syntax?
It handles classic five-field cron, which is what crontab, most CI services and cloud schedulers use. Six or seven-field formats with seconds, and Quartz extras such as L and W, are reported rather than guessed.
Is my schedule sent anywhere?
No. The expression is read and the run times are calculated in your browser. Only your last expression is remembered on this device.