You can add weekly or day wise schedule for store operation time for each store from store add/edit page.
If you add schedules to any store and enabled to capture delivery/pickup time then it wont accept the time slots other than schedule added.
We allow adding multiple slots for same day, suppose you want to operate from 9-12 am and 9-12 pm on Monday , so you will add two schedules for same day with different time slots.