Google celebrated its 20th birthday on Thursday, which is actually kind of weird, since that’s not when the company behind the search engine was incorporated. Or when its signature search engine launched. Or when it registered the domain ‘google.’ In fact, after poking around and asking the company for comment, we’re not sure what the September 27 date refers to at all.

Let’s start with some process of elimination. The company was incorporated on September 4, 1998, the closest significant date that matches up with the declared anniversary. Google actually launched a little earlier in August 1996 according to Wired.. September 27 also doesn’t refer to the date that the “google.com” became official, either, as the Washington Post reported that the web address was registered on September 15, 1997.

The company itself has in the past acknowledged that the date is a little fuzzy, stating on its doodle page that it was founded “20 (ish) years ago.” Over the years it’s decided to celebrate on the 8th, the 7th and the 26th, seemingly deciding to stick with the 27th ever since its eighth birthday back in 2006.

Google's 20th birthday doodle.
Google's 20th birthday doodle.

The Independent suggested in 2013 that the discrepancy may come from a 2005 argument with Yahoo. It goes back to Anna Patterson, founder and managing partner of Google’s A.I. fund Gradient Ventures, who back in 2005 was working as director of engineering. The publication reported at the time that Yahoo surprised Google by announcing its index of catalogued websites that was larger than Google’s. In Patterson’s rush to announce an expanded search engine index, she referred to the changes in a blog post as a “birthday” overhaul. Google seems to have stuck with this date ever since, even as its competitor Yahoo turned to Microsoft in 2009 to power its search facilities, effectively ending the index dispute between the two.

But even that story leaves us with some questions. The first time Google marked its birthday with a doodle was in 2002, when it decided on the 27th a full three years before the alleged dispute. Another issue with that story is that Patterson didn’t actually publish the post on the 27th. It went live on the 26th, a date that Google only used once as its birthday, the same year the blog post went live.

For the most part, it seems Google has been quite happy to indulge in the confusion. Search Engine Land notes that in 2006, it changed its website to no longer claim that September 7 is its birthday, instead leaving a note that the company “opened its doors in September 1998,” but “the exact date when we celebrate our birthday has moved around over the years, depending on when people feel like having cake.”

Inverse has contacted Google and Patterson for comment and we will update if someone gets back to us on this.

Photos via Google