In iPhone/iPad, you are able to set a scheduled time length for Do Not Disturb. And this article introduces how to schedule quiet hours for this mode in detail.
Steps to schedule quiet hours for Do Not Disturb in iPhone/iPad:
Step 1: Open Settings and choose Do Not Disturb.
Step 2: Turn on Scheduled.
Step 3: Set Quiet Hours.
For illustration of the above three procedures, please refer to the following screen shot.
