Cron Expression Explainer

Make sense of any cron schedule

Cron expressions are compact but easy to misread, and a single wrong field can mean a job runs every minute instead of once a day. Paste an expression here and this tool breaks down each of the five fields in plain English and shows you the next five times it will actually fire in your local timezone — so you can confirm a schedule before deploying it.

The five fields

A standard cron expression has five space-separated fields, in this order:

• Minute (0–59)
• Hour (0–23)
• Day of month (1–31)
• Month (1–12)
• Day of week (0–7, where both 0 and 7 mean Sunday)

Each field accepts * (every value), a list (1,15,30), a range (9-17), or a step (*/15 = every 15). You can combine them: 0-30/10 means 0, 10, 20, 30.

Common examples

• */15 * * * * — every 15 minutes.
• 0 9 * * 1-5 — at 9:00 AM, Monday through Friday.
• 0 0 1 * * — at midnight on the first of every month.
• 30 2 * * 0 — at 2:30 AM every Sunday.

Shorthand macros also work: @daily, @hourly, @weekly, @monthly and @yearly expand to their five-field equivalents.

The day-of-month / day-of-week gotcha

One rule trips up almost everyone: when both the day-of-month and day-of-week fields are restricted (neither is *), cron runs when either matches, not both. So 0 0 13 * 5 fires on the 13th of the month and on every Friday — not only on Friday the 13th. This explainer applies that rule when computing the next run times, so what you see is what cron will really do.

Test before you ship

The next-run preview is the fastest way to catch a mistake. If a schedule you thought was "once a day" shows runs a minute apart, you'll see it immediately. Pair this with our other DevOps helpers — validate the job's config with the JSON formatter or YAML converter before deploying.