On OS X, Do Not Disturb will automatically shut itself off the next day, so you don’t have to remember to switch notifications back on. On iOS, it works a little differently if you turn it on manually. If you have no schedule set, you have to manually turn Do Not Disturb off. If you do have a schedule set, however, Do Not Disturb will shut off automatically at your regularly scheduled time. If you have a regular schedule, you can use the manual switch to turn Do Not Disturb off before your usual time if you so choose, and it will still shut itself off at the scheduled time.