Cron Expression Syntax Cheatsheet

A cron expression has five fields, separated by spaces. Asterisk is a wild card character and means "any value."

*	*	*	*	*
					Day of week, 0 - 7, 0 or 7 is Sun
				Month, 1 - 12
			Day of month, 1 - 31
		Hour of day, 0 - 23
	Minute, 0 - 59

Use numeric values instead of asterisks to match specific minutes, hours, days, and months.

0	18	*	*	5
					Run only on Fridays
				Run every month of the year
			Run every day of the month
		Run at 6 PM
	Run at the start of the hour

Use {v1},{v2},...,{vn} to list multiple values.

0	9,12,18	*	*	*
					Run on every weekday
				Run every month of the year
			Run every day of the month
		Run at 9 AM, 12 PM and 6 PM
	Run at the start of the hour

Use {start}-{end} to define a range of matching values.

*	*	*	*	1-5
					Run from Monday to Friday
				Run every month of the year
			Run every day of the month
		Run every hour of the day
	Run every minute of the hour

Use {start}-{end}/{step} or */{step} to define a range with a step.

*/15	*	*	*	*
					Run on every weekday
				Run every month of the year
			Run every day of the month
		Run every hour of the day
	Run every 15 minutes

In the comma-separated lists, you can combine not only numeric values but also ranges.

0	18-23,0-8	*	*	*
					Run on every weekday
				Run every month of the year
			Run every day of the month
		Run at 6 PM, 7 PM, 8 PM, ..., 7 AM, 8 AM
	Run at the start of the hour

JAN-DEC can be used in the month field and MON-SUN in the weekday field.

0	*	1	APR	*
					Run on every weekday
				Run in April
			Run on the first day of the month
		Run every hour of the day
	Run at the start of the hour

The cron daemon uses the server's local time. If your server's timezone is other than UTC, make sure to set a matching timezone for your check on UGA PD Healthchecks as well.

On Ubuntu systems, you can check the server's timezone with:

cat /etc/timezone