In its quest for
world domination adequacy, Microsoft has an Android variant of its well-known Outlook email client. In fact, it's a decent app. Among other things, it has a built-in calendar. However, unlike some other calendar clients—like Microsoft-owned Sunrise—you cannot have events from places like Wunderlist in your Outlook calendar. With its latest update, though, Outlook now supports "calendar apps," which is just a not-that-fancy name for third party services that it can add to your calendar. The initial rollout includes Wunderlist, Facebook, and Evernote, which are as good of a trio as you could hope for.
Of the three, I only use Wunderlist, so on the right-hand side you have a look at how those tasks render in the calendar. Much like they do on Sunrise, they appear as all-day events. When you are finished, they get a little check mark next to them, but stay on the calendar for posterity's sake.
Another aspect of the update that is unrelated to the calendar is support for .eml file attachments. If you don't know what those are, they're email files, best known as a default file type introduced by Outlook (for desktops). I'm not sure how many people are out there emailing emails, but if you're one of those special people, you're in luck.