PP/PI: Rescheduling process order

Hi Gurus,

I have a process order for which when I go for batch determination for one material of that process order it doesn't pick up a batch for material. I diognised that there is selection criteria says Batch delivery date should be 1 days less than expiry date.

It picks up finish date as delivery date and not the starting date. So I want to reschedule order and want to change the finish date to today's date. But order doesn't reschedule?

I mean when I change the date manually and save it order itself change the date to previous one. Can anyone explain me why it happens?

Thanks in anticipation.

RajaRam