Cron expression and time expression

FastCron accepts both

• standard cron expressions like */5 * * * *
• simple time expressions like 5 minutes.

It will automatically check the expression and calculate the next execution times.

Crontab expression

The standard crontab expression consists of 5 fields:

minute hour day month weekday

Field	Allowed values	Allowed special characters
minute	0..59	*/,-R
hour	0..23	*/,-R
day	1..31	*/,-L
month	1..12	*/,-
weekday	1..7 (Mon..Sun)	*/,-

There are multiple ways to set the values for each field:

• Use * to select all allowed values
• Use */n to select all values with a step number n
  • */5 in the minute field will select from 0, 5, 10, to 55
  • */2 in the day field will select from 1, 3, 5, to 27, 29, 31
• List all values with commas 1,2,3,4,5,6,7
• Use a simple range like 1-7
• Use a simple range with a step like 1-7/2
• Use L at the day field to select the last day of the month
• Use R to select one random value
• Use R,values to select one random value from a list e.g. R,1-7 will select one random value from 1 to 7.

Your cronjob will run when the current time matches ALL the fields of the cron expression. For example, cronjob with the expression 30 7 * 10 Mon will run in October, every Monday at 07:30.

If you select specific value(s) for both the day and weekday fields, it will run when the current time matches EITHER values. For example, 30 7 15 10 Mon will run in October, at 07:30 every Monday AND at 07:30 Oct 15. You may want to use the cron expression 30 7 * 10 Mon with the time filter day == 15 to run only Monday, Oct 15.

If you’d like to run a cronjob at a specific time, see one-time cronjobs.

Due to the limitation of the time values, some cron expressions are impossible (time never matches), some time intervals e.g. every 48 minutes are not available, and some time interval can’t match perfectly e.g. every 2 days. You should try using the time expression to fit your requirements.

Here are some popular cron expressions:

Expression	Meaning
* * * * *	Every minute
*/2 * * * *	Every 2 minutes
*/5 * * * *	Every 5 minutes
*/10 * * * *	Every 10 minutes
*/15 * * * *	Every 15 minutes
*/30 * * * *	Every 30 minutes
5 * * * *	Every hour
5 */2 * * *	Every 2 hours
5 */3 * * *	Every 3 hours
5 */4 * * *	Every 4 hours
5 */6 * * *	Every 6 hours
5 */8 * * *	Every 8 hours
5 0,12 * * *	Twice a day
5 7 * * *	Every day
5 7 */2 * *	Every 2 days / Every other day
5 7 */3 * *	Every 3 days
5 7 * * 1	Every week, on Monday at 07:05
5 7 15 * *	Every month, on day 15, at 7:05

Time expression

FastCron also supports simple time expressions like 5 minutes or next Friday 7:05 PM.

Internally, it uses the PHP function strtotime. It works by calculating the next execution times based on the current execution time.

If you enter a specific time e.g. `Oct 16, 2024 07:50 PM’, then it will run only once.

Here are some popular time expressions:

Expression	Meaning
10 seconds	Every 10 seconds
30 seconds	Every 30 seconds
1 minute	Every minute
5 minutes	Every 5 minutes
14 minutes	Every 14 minutes
1 hour	Every hour
7 hours	Every 7 hours
1 day	Every day
1 day 17:05	Every day at 17:05
2 days	Every 2 days
2 days 17:05	Every 2 days at 17:05
next Friday 17:05	Every week, on Friday at 17:05
2 weeks Friday 17:05	Every 2 weeks, on Friday at 17:05
1 month 17:05	Every month at 17:05
first day of next month 17:05	Every first day of the month, at 17:05
last day of next month 17:05	Every last day of the month, at 17:05

If you need help choosing the right cron expression, email me and I’ll help.