Photo by Kuhlmann/MSC via Wikimedia.

Bill Gates is moving on.

In an after-hours filing, Microsoft Corporation MSFT announced that Gates will depart the company's board of directors to "dedicate more time to his philanthropic priorities including global health, development, education, and his increasing engagement in tackling climate change."

Microsoft was founded by Gates and Paul Allen on April 4, 1975. The company developed the MS-DOS operating system and in 1985 debuted its graphical Windows platform. The company hit the stock exchange in 1986 and now has a market cap of over $1.2 trillion.

In a separate filing, Berkshire Hathaway (NYSE: BRK-A) (NYSE: BRK-B) also announced Gates will leave its board and will be replaced by Ken Chenault. Gates has been a close friend of Warren Buffett for several decades.

“I believe in investing in what you understand,” Buffett said back in 2015. “I met Bill Gates on July 5, 1991, and we actually talked for 10 hours that day. He was explaining his business to me and I was explaining what I do to him. When I got all through, I bought 100 shares of Microsoft just to keep track of him.

"Now if I'd bought 100,000 shares -- or 100 million shares -- that would have been a lot more sensible," Buffett joked.