Android 5.0 introduced recurring downtime as part of the new notification control scheme, and Android 5.1 brings an important enhancement to this system. You can now choose whether you want programmed downtime to trigger priority mode or block all notifications. It's all right there in the downtime settings, which you still have to dig for.
Left: 5.0, Middle and right: 5.1 Read More
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. Read More