Opening hours of product templates and subproduct templates can be stored directly on the respective template.
If you have two different opening times on a Monday, for example on Mondays from 11 am to 1 pm and from 7 pm to 11 pm, then you store one opening time on Monday at noon and a second one in the evening.
If you do not enter opening hours, the 24 hours simply apply. You do not have to enter opening hours from 00:00 - 23:59.
Holidays are entered globally into the system here: Holidays.