Business / Technology

Microsoft is adding another mobile productivity app to its quiver.

The company says it has acquired Sunrise, a maker of calendar apps for Apple’s iOS and Google’s Android mobile operating systems. The deal comes two months after the purchase of Acompli, a popular builder of email apps that Microsoft later used as the base for new Outlook email apps for those operating systems.

Microsoft, whose Windows platform accounts for a tiny share of the global tablet and smartphone markets, has been trying reaching customers on competing platforms. In November, the company unveiled free versions of some of its Office productivity suite for iOS and Android, and has since completed the Acompli and Sunrise deals to bolster its ability to build products for those platforms.

Rajesh Jha, a vice president with Microsoft’s Outlook and Office group, said in a blog post that the company planned to keep Sunrise free of charge and available to download. Jha didn’t disclose the terms of the purchase.

Microsoft, it shouldn’t be a surprise, has acquired mobile email app maker Acompli.

The company accidentally teased the deal last week, publishing a blank shell of a blog post evidently meant to announce the purchase.

Acompli’s app, available on iOS and Android, is designed to help people navigate and prioritize email, keep track of files sent as attachments and better organize calendar functions. The app is one of a set of new tools giants such as Google and startups are rolling out to help people clean up an at times overwhelming email load.

Under a program that runs March 8 to June 30, Microsoft is paying developers $100 for each app — up to a maximum of 10 per store — that they publish in the Windows Store or Windows Phone Store. (To participate in the program, developers must be legal U.S. residents and be U.S. registered Windows…