Maintenance Plan scheduling

Dear Experts ,

We know that system will postpone & reschedule the next maintenance plan date if the existing maintenance plan got delayed by few days.

We also know that it can be achieved by using shift factor.

I just wanted to know which date mentioned in present maintenance plan will system consider in order to reschedule the next maintenance plan.

Will it consider reference date or technical completion date or some other date ?

Regards

Keerthan Kumar