Sunrise supports a number of features you’d want to organize events, including recurring appointments, alerts, birthdays, Google Maps directions, and more. Sunrise currently supports Gmail accounts and Facebook events / birthdays from the social network. The iOS and Android calendar app also integrates well with popular services like SongKick and TripIt to map upcoming gigs and help plan trips. There’s even Foursquare integration to see a history of places you’ve visited, and Evernote features to let you view reminders inside Sunrise. So Microsoft's interest in Sunrise is understandable, it's simply the Swiss Army knife of calendar apps.
It’s not clear how Microsoft plans to use Sunrise in future, but it’s reasonable to expect the company will fold the features into its Outlook app. Outlook on iOS and Android has its own calendar, but Sunrise’s features are a lot more powerful so it would make a lot of sense to combine the two. The acquisition is yet another step in Microsoft's plan to own productivity across multiple platforms, and expand its mobile Office suite.