But why did Google throw its party today? Turns out the precise moment of Google's anniversary is hard to pin down.
Google had many early milestone in September, none of which land on the 27th. The google.com domain name was registered on September 15, 1997. The company was incorporated on September 4, a year later. It opened its office doors on September 7.
In fact, in 2004 and 2005, Google celebrated its birthday on September 7. Many people thought the bouncing balls logo from Sept. 7, 2010, was a return to the earlier birthday.
In the end, Google spokesman Jordan Newman says there is no real reason behind the 27th. It just seemed like a good day to celebrate Google's founding.
"There's many dates we could choose in September – the day we incorporated, when the first employee was hired, or even when the Google.com domain was registered," says Mr. Newman. "That's why we consider September our 'birthday month.' "
So, with this cake under our belts, what's been your favorite Google doodle of 2010? The Hans Christian Andersen flipbook? Those bouncing balls? Maybe Frida Kahlo? Perhaps the Pac-Man game/doodle? (And did you know you can still play Google Pac-Man for free?) Something else? Let us know in the comments.