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Cron explainer

When does it run?

Linux crontab syntax: minute, hour, day of month, month, day of week. Calculated in your browser.

Every 5 minutesEvery hourDaily at 02:30Weekdays at 07:00Every 15 min, business hoursSundays at 03:001st of the month, 06:00QuarterlyTwice a day

At 02:30

30Minute
2Hour
*Day of month
*Month
*Day of week

Next runs (Europe/Vienna)

  1. Sat 2026-10-17 02:30
  2. Sun 2026-10-18 02:30
  3. Mon 2026-10-19 02:30
  4. Tue 2026-10-20 02:30
  5. Wed 2026-10-21 02:30
  6. Thu 2026-10-22 02:30
  7. Fri 2026-10-23 02:30
  8. Sat 2026-10-24 02:30
  9. Sun 2026-10-25 02:30
  10. Mon 2026-10-26 02:30

Times skipped by a daylight-saving change are not listed (cronie runs them right after the switch).

Details

Minute30
Hour2
Day of month*every
Month*every
Day of week*every

systemd timer

OnCalendar=*-*-* 02:30:00

Syntax

┌───────────── minute        0–59
│ ┌─────────── hour          0–23
│ │ ┌───────── day of month  1–31
│ │ │ ┌─────── month         1–12 or JAN–DEC
│ │ │ │ ┌───── day of week   0–7 or SUN–SAT (0 and 7 = Sunday)
│ │ │ │ │
* * * * *  command
*
every value
1,15
list
1-5
range
*/15
every 15th value (0, 15, 30, 45)
8-17/2
every 2nd value within a range
@daily
@hourly, @daily, @weekly, @monthly, @yearly, @reboot

If both day of month and day of week are restricted, cron runs when either matches. Cron uses the server's time zone (or CRON_TZ= in the crontab).

Same in the terminal

$ curl tools.otw.solutions/cron/30_2_*_*_*

Or with spaces: curl "tools.otw.solutions/cron?e=0+3+*+*+1-5" · JSON: add ?format=json