When does it run?

Give a cron expression or an RRULE and a time zone, and see the rule in words and its next runs, through the nights the clocks change. Time::Keeper::Recurrence walks the rule.

Cron or RRULE

Time zone

Start, for an RRULE

Runs

Try

0 9 * * 1-5 weekdays at nine
*/15 9-17 * * 1-5 every 15 minutes in working hours
FREQ=MONTHLY;BYDAY=1MO the first Monday of the month
FREQ=MONTHLY;BYMONTHDAY=-1 the last day of the month
30 2 * * * 02:30, on a night the clocks change
30 1 * * * 01:30, through the hour that comes twice