When Google released the first Android M preview images shortly after Google I/O, one of the bigger changes was a reworking of the priority interruptions system that was part of Lollipop. It went back to being called Do Not Disturb mode again in M, but one of the handier features of the system was tossed: the ability to mute notifications until your next scheduled alarm.
This feature is, obviously, convenient for a variety of reasons.
Android 6.0.1 Brings Back The "Until Next Alarm" Option For Do Not Disturb Mode was written by the awesome team at Android Police.
Source: Andriod Police