Software titan Microsoft is acquiring startups that have created rival products, and its latest acquisition is calendar app maker Sunrise, for which Microsoft paid at least $100 million.

TechCrunch reports Sunrise is popular with consumers because it is much easier to use than the standard calendar app that comes with most smartphones. The free app has the familiar date grid but added a scrollable events list, while also connecting to social media accounts to integrate information about contacts and events. Sunrise launched two years ago on the iPhone where it received critical acclaim. Soon after, it expanded to iPad, Android, Mac and the web.

Sunrise is highly regarded as the best calendar app for iPhone, iPad, Android devices and the desktop amongst users. It syncs with all the major services like Apple iCloud, Google and Exchange and also seamlessly links with LinkedIn, Twitter, Facebook and Foursquare for events and notifications.

Microsoft will offer the Sunrise apps as stand-alone products, while using the startup's technology for its own products-the same strategy the company used when it acquired Latino-founded email app Acompli; when Microsoft launched its most recent Outlook for Android and iOS apps last week, the new applications were based on Acompli technology.

The purchases demonstrate that Microsoft is investing big time in the mobile productivity space. The company clearly aspires to support the platforms of rival technology companies.

Since Outlook has its own calendar, one can only speculate where Sunrise stands with regard to Acompli/Outlook. It could be integrated with Acompli. No matter what happens to Sunrise, Microsoft is acquiring outstanding mobile talent so that it can expand from monolithic desktop applications to embrace a more versatile future.

Sunrise investors, who had only chipped in $8.2 million, are celebrating a great pay day.

Sunrise was founded in 2012 by two former Foursquare designers, Pierre Valade and Jeremy Le Van.