dmosk / cronius

Cron expression builder and decoder

Type a cron expression or assemble it with the field builder, read what it means, check the next runs in your time zone, and copy a systemd timer or Kubernetes CronJob snippet. Everything runs in the browser — no API.

Examples

Field builder

Minute
Hour
Day of month
Month
Day of week

Benefits

  • Plain-language description in your interface language, so you can check a schedule at a glance.
  • Next runs table with an explicit time zone — browser, UTC or a common IANA zone.
  • Ready OnCalendar and CronJob snippets with an honest note about the differences.

How to use

  1. Enter a cron expression or pick an example such as every minute or weekdays at 9:00.
  2. Or set each field with the builder: every, specific values, a range or a step.
  3. Choose a time zone and how many upcoming runs to show.
  4. Copy the systemd or Kubernetes snippet, or share the link with ?expr= and ?tz=.

Cron tips

Short notes that save debugging time:

Tips

  • If both day of month and day of week are restricted, classic cron runs when either matches.
  • Cron uses the server time zone; DST changes can skip or repeat a run, so pin the zone explicitly where you can.
  • systemd OnCalendar and Kubernetes timeZone are close to cron but not identical — verify with systemd-analyze calendar.

What it is for

  • Checking a crontab line before it goes to production.
  • Moving a job from cron to a systemd timer or a Kubernetes CronJob.
  • Explaining a schedule to a teammate and sharing it as a link.

FAQ

What does */5 mean?

Every 5 units of that field starting from its minimum. In the minute field it means every 5 minutes: 0, 5, 10 and so on.

Are 0 and 7 both Sunday?

Yes. In the day-of-week field 0 and 7 are Sunday. Names JAN–DEC and SUN–SAT are accepted in any letter case.

Will systemd and Kubernetes behave exactly like cron?

Not always. The snippets are a best-effort conversion; time zones, DST and missed runs differ, so test them in the target system.

Is my expression sent to a server?

No. Parsing, the description and the next runs are calculated in your browser. A shared link only carries the expression and the time zone in the URL.