For those who installed this add-on and some Cron extension in Joomla.
link
Predefined scheduling definitions
Several special predefined values can be substituted into the cron expression. Note that in some uses of the cron format (e.g. Quartz), there is also a seconds field at the beginning of the pattern.
Entry Description Equivalent to
@yearly (or @annually)
Run once a year at midnight on the morning of January 1 0 0 1 1 *
@monthly
Run once a month at midnight on the morning of the first day of the month 0 1 * *
@weekly
Run once a week at midnight on Sunday morning 0 0 * * 0
@daily
Run once a day at midnight 0 0 * * *
@hourly
Run once an hour at the beginning of the hour 0 * * * *
@reboot
Run at startup @reboot
# * * * * * command to execute
# │ │ │ │ │
# │ │ │ │ │
# │ │ │ │ └───── day of week (0 - 6) (0 to 6 are Sunday to Saturday, or use names; 7 is Sunday, the same as 0)
# │ │ │ └────────── month (1 - 12)
# │ │ └─────────────── day of month (1 - 31)
# │ └──────────────────── hour (0 - 23)
# └───────────────────────── min (0 - 59)
