Microsoft has announced that they have acquired Sunrise, a calendar application that the company hopes will boost your productivity. While the company has not shared the details of the price paid, a recent rumor suggested that it cost the Redmond based company over $100 million.

The app is clearly popular with those who use it and it's likely because of this popularity that Microsoft took an interest. As the company looks to make sure it has the best applications on all platforms, it appears that it is on a buying spree to build out its portfolio.

This app, like the Outlook email app, is offered for free, which does present an issue of how the company plans to increase revenue with these applications. It could be that they are planning to use them as loss-leaders to get more users into the Microsoft ecosystem with the hope that they will subscribe to one of the many services offered by the company, like Office 365.

The purchase is a bit interesting too, as the company's new Outlook application already has a robust calendar built into the app; this purchase does seem to have some redundancy to it.

We will be curious to see if Microsoft rebrands the app like they did with Acompli that got renamed to Outlook and then re-released to the various app stores. The company did say that the Sunrise app will remain in the app stores and free after the acquisition; they will share more about future plans in the coming months.