Cron Expression Tester

From left to right: minute (0–59), hour (0–23), day of month (1–31), month (1–12 or JAN–DEC), and day of week (0–7 or SUN–SAT, where both 0 and 7 mean Sunday). Each field accepts a value, a list (1,15), a range (9-17), a step (*/5) or * for "any". The expression "30 2 * * 1" therefore means: at 02:30 every Monday.

Use */5 * * * * — the */5 step in the minute field matches minutes 0, 5, 10, … 55. The same pattern works in other fields: 0 */6 * * * runs every 6 hours on the hour, and 0 0 */2 * * runs every second day at midnight (based on the day number, so month boundaries can produce a 1-day gap).

You can't — standard cron has no "every N weeks" concept; the day-of-month and day-of-week fields reset every month, so a true 14-day interval isn't expressible. The closest approximations: 0 0 1,15 * * (the 1st and 15th — twice a month, which is what most people actually want) or run the job weekly and let the script decide: exit early unless the ISO week number is even. If you're on systemd, timers support real biweekly schedules natively via OnCalendar.

Classic (Vixie) cron treats them as OR, not AND: "0 0 1 * 1" runs on the 1st of the month AND on every Monday — whichever comes first. This surprises almost everyone. If you need "the first Monday of the month" you can't express it in standard cron; schedule every Monday and check the date in your script.

Yes — both mean Sunday. POSIX cron defines day-of-week as 0–6 starting at Sunday, but Vixie cron (what Linux distributions ship) also accepts 7 for Sunday. This tester accepts both and normalises 7 to 0.

The timezone of the machine (or container) running the cron daemon — often UTC on servers, which is why a job scheduled for 0 9 * * * fires at 9:00 UTC, not 9:00 your local time. Some systems support CRON_TZ=Europe/Vilnius at the top of the crontab. The preview on this page uses your browser's local timezone, shown next to the run times.

Standard Unix cron does not — the smallest unit is one minute. Six-field expressions with a leading seconds field come from Quartz (Java) and some cloud schedulers. If a tool rejects your 6-field expression, drop the first field. For sub-minute scheduling, use a loop with sleep, a systemd timer with OnCalendar, or your platform's native scheduler.

The most common causes: the cron daemon uses a different timezone than you expected; the PATH inside cron is minimal so commands that work in your shell fail (use absolute paths); the crontab line is missing a newline at the end; %-signs weren't escaped (cron treats % as newline); or the machine was off at the scheduled time (plain cron doesn't catch up — anacron does). Silent failures are exactly why teams add heartbeat monitoring to critical jobs.

@reboot runs a command once when the cron daemon starts — usually at machine boot. It has no time schedule at all, so there are no "next runs" to compute. The other aliases map to normal schedules: @hourly is 0 * * * *, @daily is 0 0 * * *, @weekly is 0 0 * * 0, @monthly is 0 0 1 * *, and @yearly is 0 0 1 1 *.