Google declared September 27th its "official" birthday with a 15-year celebration last year, though a precise date for the start of the company isn't really known. Today Google has taken to its homepage and official Twitter account to celebrate the date.
You could say that the start of Google goes back at least 18 years to when Larry Page and Sergey Brin began work on their custom "BackRub" search engine at Stanford University. The company was officially incorporated on September 4th, 1998, though an earlier version of Google was posted on Stanford servers before then.
Today our cake has 16 candles (+1 to grow on). #OkGoogle http://t.co/xnDLg1B86X
— A Googler (@google) September 27, 2014
Google has since then gone on to introduce the world to Android, which celebrates it official birthday on November 5th. This commemorates the day that Google introduced the Open Handset Alliance in 2007, though the original "Android" company was started by Danger Inc. co-founder Andy Rubin and others way back in 2003 and acquired by Google two years later.
source - Google