Cron Expression Explainer

Cron schedules jobs on Linux servers, in CI pipelines such as GitHub Actions, and in Kubernetes CronJobs, using five terse fields that are easy to get wrong. This explainer reads a standard cron expression, describes it in plain English, shows the values each field allows, and lists the next eight times it will run in your time zone or in UTC. It follows the classic crontab rules, including the one that catches most people: when both day of month and day of week are restricted, the job runs when either one matches.

1. Type or paste a cron expression, or pick an example.
2. Read the plain-English meaning and check each field underneath the input.
3. Look at the next runs to confirm the schedule does what you expect.
4. Switch between your local time and UTC — most servers and CI systems run cron in UTC.
5. Copy the expression when it’s right.

• This is standard five-field cron as used by crontab, GitHub Actions and Kubernetes. Six- or seven-field formats with seconds or years (Quartz, Spring, AWS EventBridge) are not supported, and neither are the extensions L, W, # and ?.
• Run times are shown in your device’s time zone or UTC. A server in another zone will run at a different wall-clock time.
• Around daylight-saving changes, real cron daemons may skip or repeat a run in the missing or repeated hour; the list here doesn’t model that.
• @reboot runs at startup and has no schedule to show.
• The expression is parsed and the run times calculated in your browser. Nothing is sent or saved.

Every 15 units starting from the lowest value — in the minute field, at 0, 15, 30 and 45. 5/15 starts at 5 instead: 5, 20, 35 and 50.

Because it sets both day of month (1) and day of week (Friday). Cron treats that as OR, so it runs on the 1st and on every Friday. To run only on Fridays that are the 1st, check the date inside your script.

Both. 0 and 7 mean Sunday, and names such as MON or fri work too.

GitHub Actions uses UTC, and scheduled runs can be delayed during busy periods. Switch the next runs to UTC to see the times GitHub uses; 9:00 IST is 30 3 * * *.