This is Google's new "Nexus Launcher"

According to multiple reliable sources, we believe that Google plans to debut a brand-new launcher for Nexus devices some time in the near future, likely on its 2016 Nexus (if they are Nexuses) smartphones Marlin and Sailfish.That unremovable date widget is an absolutely dreadful idea. Luckily though, this is Android, so you can replace it with whatever launcher you want.