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Cron Expression Parser

Decode cron expressions with the next run times, in your local timezone.

Runs locally in your browser

// human readable

At 09:00, Monday to Friday.

0
minute
9
hour
*
day of month
*
month
1-5
day of week
// next 5 runs

Working it out.

Want to know why a schedule behaves the way it does? The cron expression simulator runs the same engine with the traps laid out: uneven steps, the two day fields, and what daylight saving does to a job in the small hours.

How it works

Cron syntax cheat sheet

Five fields, in order

* * * * *
┬ ┬ ┬ ┬ ┬
│ │ │ │ └─ day of week (0-7, Sun=0 and 7)
│ │ │ └─── month (1-12)
│ │ └───── day of month (1-31)
│ └─────── hour (0-23)
└───────── minute (0-59)

Operators

  • * any value
  • , list of values, e.g. 1,15,30
  • - range, e.g. 1-5
  • / step, e.g. */15 every 15
  • Names work too: JAN-DEC and SUN-SAT

The one that catches everyone

When both the day-of-month and day-of-week fields are set, cron combines them with or, not and. 0 9 1 * MON runs on the 1st of the month and on every Monday, not only on Mondays that fall on the 1st. A monthly job written that way quietly runs weekly. If only one of the two is set, it behaves as you would expect.

Shortcuts

  • @yearly / @annually: 0 0 1 1 *
  • @monthly: 0 0 1 * *
  • @weekly: 0 0 * * 0
  • @daily / @midnight: 0 0 * * *
  • @hourly: 0 * * * *

Frequently asked questions

What does * * * * * mean?

Every minute of every hour of every day. The five fields are minute, hour, day-of-month, month, day-of-week. An asterisk in any field means "any value".

How do I run a job every 15 minutes?

Use `*/15 * * * *`. The slash introduces a step value; `*/15` means every 15 minutes starting at minute 0.

What timezone do the next run times use?

Your local timezone, as reported by the browser. If your server runs cron in UTC, remember to adjust before scheduling.

Are @daily and 0 0 * * * the same?

Yes. `@daily` and `@midnight` are shortcuts for `0 0 * * *`. This parser expands them automatically when computing the next run times.

Tools are ported from DevOps Daily under the MIT license.View original

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