Your hours decide when your booking page offers times. Every account starts on a standard week, so you can open your page without touching them; press Keep these hours on the Setup Guide to say so, or set your own under Settings → Hours.
The weekly pattern
Open and close times for each day, and the days you're shut. This is the business's week: everyone works it unless they have their own hours. You can still add a booking outside it; you'll see a warning first.
Each person's hours
A team member can have their own days and times, on their Team profile. Their own hours replace the business's week for them: someone who works Tuesday to Saturday only shows times on those days, even if the business is open Monday, and someone who works a Sunday can be booked on a Sunday even though the business is closed. See Add your team.
For rotating weeks, time away and different hours on a date, see Rosters, rotating weeks and the dates that differ.
Days you're closed
Public holidays and your own closed dates come out of the calendar in one place; see Closed dates and public holidays. A single person's holiday or sick day is time away, which takes them out without closing the business.
Changing hours later
A change applies from now on. Anything already booked stays where it is, even if it now sits outside the new hours; move or cancel it yourself if you need to. If a time you expect isn't showing on your page, this article walks through why.