How quiet hours work
Quiet hours hold non-urgent push notifications overnight instead of turning them off outright. It is one switch in Preferences, with a start and end time under it.
Turning it on
In Preferences, under Quiet hours, flip the Quiet hours switch on. Two rows appear underneath, From and Until, each with a − and + button that step the time by 30 minutes. The window can wrap past midnight — stepping Until earlier than From is how you set an overnight window rather than a same-day one.
What it actually holds back
Quiet hours only affects push notifications, and only non-urgent ones. Anything in the four notification categories — New orders, Order updates, Reminders, Account notices — is held if it falls inside your window. A notification held this way still lands in your in-app inbox; it just does not push to your phone until the window ends.
Critical alerts push regardless of the window. Nothing about your sales gets silently delayed.
It needs a timezone to mean anything
A quiet window is stored with the timezone it was set in. The app writes your device's current timezone every time you save a change on this screen, so using the toggle from your phone or browser is enough — you never set it by hand. But a window recorded without a timezone is not enforced at all rather than guessed against server time, so it only works once it has actually been saved from a device.