File this one in the long list of small but nonetheless significant Android 5.1 improvements. In Lollipop, when you try changing the phone's volume, you get 3 different modes: None, Priority, and All. For better or worse, it's still the case in Android 5.1 with one minor addition: alarms are now integrated as a deadline option.
Left: 5.0 no alarm option. Middle & Right: 5.1 alarm option for None and Priority modes.
On Android 5.0, if you pick no interruptions or only priority ones, you can set an end time when your device will go back to showing all notifications. That is either indefinitely, for a specific amount of time, or until your downtime ends. On 5.1, "until next alarm" shows up as well. That makes a lot of sense. After all, you don't want to fiddle with manually picking up the exact times twice on your phone. You just set up your alarm, and silence most or all of your notifications until then.
You'll notice that the interface is also slightly less condensed, with clearer end times and prominent icons for each volume mode. And before you ask, no, there's still no proper silent mode. Go use SoundHUD instead.
- Ramit Suri