Microsoft has acquired calendar startup service Sunrise for around $100 million, one of a flurry of new acquisitions from Microsoft for standalone services.

Sunrise has become one of the go-to calendar apps on iOS, Android and any other platform, an excellent cross-platform solution to note-taking and schedule checking.

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The startup-headquartered in New York City-has been working on calendar services since 2012, receiving initial seed funding and Series A funding with a valuation of $50 million.

Microsoft will let the Sunrise Calendar service continue to exist post-acquisition, and will work to integrate the calendar service with its own application on Windows Phone and Windows 10.

Sunrise Calendar does not offer a Windows Phone or Windows 8 app, but has desktop and browser based clients. It is part of a growing trend from Microsoft of embracing startups that work for rival companies.

Microsoft could also integrate Sunrise Calendar into its Outlook and Office 365 suite.

The acquisition follows a $200 million acquisition for Acompli, an email application that supported Gmail and other mail services. Microsoft allows this application to stay open after the acquisition.

This might be the start of a big trend by Microsoft to acquire smaller startups, integrating more productivity apps into its already large suite. A similar tactic to Yahoo's CEO Marissa Mayer, who has been on a spending spree since she took charge of the search giant.

TagsSunrise calendar, calendar app, Microsoft acquisition