When I went to Google's search page this weekend, I saw the logo had changed to the following:

I think google knows (or thinks it knows) when your birthday is based on your Google Profile settings.

The only problem with that is that it wasn't my birthday at all. I don't put my real birthday in social media sites for security reasons. Generaly I set it to either April 1st (april fools day) or 1st January 1970 - which any programmer would immediately recognise as the Unix Time zero. Makes me a few years older but is easier to remember.