Cron expression parser and explainer

How to read a cron expression

A cron expression has five fields, read left to right: minute, hour, day of month, month and day of week. An asterisk means every value. 30 2 * * 1 runs at 02:30 every Monday, and */15 9-17 * * MON-FRI runs every 15 minutes from 09:00 through 17:45 on weekdays, 36 times a day.

The five fields

1. Minute: 0–59
2. Hour: 0–23
3. Day of month: 1–31
4. Month: 1–12, or JAN–DEC
5. Day of week: 0–7, or SUN–SAT, where 0 and 7 both mean Sunday

Each field takes * for every value, a single number, a list with commas (5,20,50), a range with a hyphen (9-17) or a step with a slash (*/15, 10-40/15). Names are case-insensitive.

The crontab(5) manual for cronie and Vixie cron defines this grammar, the format most Linux crontabs follow.

Common cron schedules

• Every 5 minutes: */5 * * * *, 288 runs a day
• Every hour on the hour: 0 * * * *, or @hourly
• Every day at midnight: 0 0 * * *, or @daily
• Every day at 02:30: 30 2 * * *
• Weekdays at 09:00: 0 9 * * 1-5
• Every Sunday at midnight: 0 0 * * 0, or @weekly
• The first of every month at midnight: 0 0 1 * *, or @monthly
• Every 1 January at midnight: 0 0 1 1 *, or @yearly

How steps work

A step counts from the start of its range and restarts every hour or day. */15 in the minute field means 0, 15, 30 and 45, and 10-40/15 means 10, 25 and 40.

Because steps restart, they are not always even intervals. */35 * * * * fires at minutes 0 and 35, so the gaps alternate between 35 and 25 minutes.

0 */5 * * * fires at 00:00, 05:00, 10:00, 15:00 and 20:00, then waits only 4 hours for midnight. To start a step elsewhere, give a range: 1-59/5 runs at minutes 1, 6, 11 and so on.

When both day fields are set

If day of month and day of week are both restricted, cron runs when either one matches. 0 12 1 * MON fires at noon on the 1st of every month and on every Monday, not only on Mondays that fall on the 1st.

In cronie and Vixie cron, a day field that starts with * switches this to AND. 0 0 */2 * FRI therefore runs only on Fridays with odd dates, because */2 counts days 1, 3, 5 and onward.

Next runs for five schedules

Default is */15 9-17 * * MON-FRI. Every row starts on 15 January 2026 at 00:00 UTC except Every five minutes, which starts at 12:35 and first fires at 12:40, because runs are listed strictly after the start.

Leap days is 0 0 29 FEB *, and the last two rows are the day-field examples above. Runs per matching day counts time slots on a day that matches, even though most years have no 29 February.

Time zones and daylight saving

These run times are in UTC. A cron daemon uses the server's local time zone unless the crontab sets CRON_TZ (in cronie).

On a daylight-saving changeover day, a job at 02:30 local time can be skipped or shifted. Servers that run on UTC avoid the problem.

Common cron mistakes

• * 9 * * * for "9 a.m." That runs every minute from 09:00 to 09:59, 60 times. Write 0 9 * * *.
• Six fields. Quartz and Spring put a seconds field first, as in 0 0/15 * * * ?. Crontab takes five fields, and ?, L, W and # belong to those other dialects.
• Wrapping ranges. 22-2 is rejected here; write 22-23,0-2 for 22:00 through 02:00.
• An unescaped % in the command. Crontab turns % in the command part into a newline, so date +%F must be written date +\%F.
• Impossible dates. 0 0 30 2 * never runs, because February has no 30th.

Supported syntax and search range

• Five fields, or one of @hourly, @daily, @midnight, @weekly, @monthly, @yearly and @annually. @reboot has no calendar time to list.
• Up to 50 upcoming runs, found by searching a full 400-year Gregorian cycle, so rules such as 2100 not being a leap year are covered.

For the gap between two calendar dates, use the date difference calculator.