Facing problem for building cron expression daily for every N days

[Gnana Prasuna]

Hi All,

I am facing problem in building cron expression for below pattern.

Daily for every three days starting on nov 09, no end date
cron expression: 0 0 0 09/3 * ? *
output is 9th,12th,15th.....

Above expression working fine before last week of month.

If i try the same expression for this paatern every three days starting on 29 nov, no end date
cron expression: 0 0 0 29/3 * ? *
output 29th nov,29th dec,29th jan, 29th mar

Can some body help me in build expreesion for handling above 2 cases.

Thanks,
Prasuna.

[Paul Clapham]

Every time I look at cron documentation, I see there's two kinds of day: there's Day-Of-Month and there's Day-Of-Week. You're experimenting with Day-Of-Month and now you have found how it behaves. Notice the "Of-Month" part in the description, that explains why it behaves that way.

If that isn't clear, then let me put it this way: from the cron documentation I have read, I wouldn't expect to be able to produce an expression which meant "every three days regardless of month boundaries".