Quartz Cron Expression
Quartz cron has 6 required fields (plus an optional year): seconds minutes hours day-of-month month day-of-week. You must use ? in either day-of-month or day-of-week because you can't specify both. The example runs at 9 AM on weekdays.
The expression
0 0 9 ? * MON-FRI fires at 09:00:00 Monday–Friday. Fields: seconds minutes hours day-of-month month day-of-week [year].
The ? placeholder
Quartz won't accept a value in both day-of-month and day-of-week — one must be ? (no specific value). Set the day-of-week here, so day-of-month is ?.
Special characters
L = last (e.g. L in day-of-month is the last day; 6L in day-of-week is the last Friday). W = nearest weekday. # = nth weekday, e.g. 6#3 is the third Friday. Day-of-week in Quartz is 1–7 with 1 = Sunday.
Common pitfalls
Using * in both day fields throws an error — use ?. And Quartz day-of-week numbering (1=SUN) differs from Unix cron (0=SUN), so prefer the three-letter names.
FAQ
How many fields does a Quartz cron expression have?
Six required (seconds minutes hours day-of-month month day-of-week) plus an optional year field, so 6 or 7.
Why does Quartz need a ? in the cron?
You can't set both day-of-month and day-of-week. One must be ? (no specific value). Set the one you need and put ? in the other.
What does L mean in a Quartz cron?
Last. In day-of-month, L is the last day of the month; in day-of-week, e.g. 6L is the last Friday. Quartz numbers days of week 1–7 with 1 = Sunday.