September 27th, 1998

For some peculiar reason, Google has at times chosen the date of September 27th as their birthday, even though it is more officially September 4th or 7th. Google has no explanation for celebrating their birthday on different days over the years other than to say:

Google opened its doors in September 1998. The exact date when we celebrate our birthday has moved around over the years, depending on when people feel like having cake.