If a shift time changes after someone confirms, should the old confirmation still count?

A cleaner confirms a 9:00 AM shift. Later, the start time moves to 11:00 AM.

I wouldn't carry the original confirmation over automatically. The cleaner agreed to the shift as it was scheduled at the time, and changing the start time may affect whether they can still make it.

I'd show the change and ask them to confirm again. Otherwise, the schedule can say "confirmed" even though they never agreed to the new time.

How does your team handle confirmations when a shift changes after someone has already accepted it?