Important! Rule timers run in GMT, so a timer that runs at hour 23 is running at 11 pm or 23:00 hours in GMT time (London, England, for example). If you are in another time zone, for example, Eastern Standard Time (Boston), then the timer runs not at 11 pm but at hour 23 minus five hours, or 6 pm (18:00 hours).
Select one of the following options:
Happens every hour - If you select this option, the timer fires every hour. When you select this option, the Cron expression in the Schedule field shows the asterisk character (*) for this field.
Happens every [12] hours -- Specify the interval of hours on which the timer should fire. The default is every 12 hours. When you select this option and specify an interval, the Cron expression shows "0/n" in this field, where "n" is the number of hours you specified for the interval. For example, if you specify every 4 hours, this field shows "0/4" in the Cron expression.
Happens from hour [0] to [23] -- This option allows you to set the timer to fire over a period of hours. Specify the hour at which you want the timer to start and the minute at which you want it to stop. For example, you might specify "from hour 22 to 23" for a timer that will fire for 1 hour, starting at hour 22 (11 PM). This field in the Cron expression would show the range as "22-23"
Happens every [12] hours, starting at hour [0] -- This default setting would cause the timer to fire two times a day, at midnight and at noon. If you choose this option and keep the default settings, this field in the Cron expression would show "0/12" to indicate that the timer starts at hour 0 and fires every 12 hours.
Other expression - This field allows you to use Cron format to type a time expression for hours. In addition, when you re-open this dialog box after making a selection, this field shows the Cron format for that selection.
When ready, click OK to save your selection and return to configuring the Schedule.