# *  *  *  *  *  [user] [command]
# |  |  |  |  |
# |  |  |  |  '---- day of week  (0 - 6)
# |  |  |  '------- month        (1 - 12)
# |  |  '---------- day of month (1 - 31)
# |  '------------- hour         (0 - 23)
# '---------------- minute       (0 - 59)

Entry           Description             Equivalent To
@reboot 	Run once, at startup. 	None
@yearly 	Run once a year 	0 0 1 1 *
@annually 	(same as @yearly) 	0 0 1 1 *
@monthly 	Run once a month 	0 0 1 * *
@weekly 	Run once a week 	0 0 * * 0
@daily 	        Run once a day 	        0 0 * * *
@midnight 	(same as @daily) 	0 0 * * *
@hourly 	Run once an hour 	0 * * * *

Examples

This line executes the "find" command at 2am on the 12th of every month that a Sunday or Saturday falls on.
0	2	12	*	0,6	/usr/bin/find

This line executes the "ping" command every minute of every hour of every day of every month and sends every output to /dev/null.
*	*	*	*	*	/sbin/ping -c 1 192.168.0.1 >/dev/null 2>&1

This line executes the "ping" command every 12am and 12pm on the 1st day of every 2nd month.
0	0,12	1	*/2	*	/sbin/ping -c 1 192.168.0.1

This line executes the disk usage command to get the directory sizes every 2am on the 1st thru the 10th of each month.
0	2	1-10	*	*	du -h --max-depth=1 /

This line is an example of running a cron job every month, on Mondays whose dates are between 15-21. This means the third Monday only of the month at 4am.
0 	4	15-21	*	1	/command

This line is an example of running a cron job every 5 Minutes from Monday to Saturday as user 'root'.
*/5 	* 	* 	* 	1-6 	root 	/path/to/command

This line is an example of running a cron job at 5am on Sunday as user 'root'.
0	5	*	*	7	root	/path/to/command

This line is an example of running a cron job every 15 Minutes.
*/15	*	*	*	*	/path/to/command

This line is an example of running a cron job on Sunday, between 12am and 12pm every 5 Minutes as user 'root'.
*/5	12-24	*	*	7	root	/path/to/command