The cron expression is made of five fields. Each field can have the following values.

*	*	*	*	*	*
minute (0-59)	second (0 - 59)	hour (0 - 23)	day of the month (1 - 31)	month (1 - 12)	day of the week (0 - 6)

Here are some example for you.

Cron expression	Schedule
* * * * *	Every minute
* * * * * *	Every second
0 * * * *	Every hour
0 0 * * *	At 12:00 AM
0 0 * * FRI	At 12:00 AM, only on Friday
0 0 1 * *	At 12:00 AM, on day 1 of the month
0 23 ? * MON-FRI	At 11:00 PM, Monday through Friday
* * * 6-8 *	Every minute, July through September
23 12 * * SUN#2	At 12:23 PM, on the second Sunday of the month
0 0 1 /3	At 12:00 AM, on day 1 of the month, every 3 months