Some of the oldest Google Easter eggs are found using the Google search function for calculations. Type 'loneliest number' in the search bar and the answer will make the songwriter Harry Nilsson smile. Type in 'number of horns on a unicorn' and Google will calculate the answer.
Fans of The Hitchhikers Guide to the Galaxy will be happy to know that Google's calculator also provides the correct response to 'the answer to life, the universe and everything'. Wondering how often we have a blue moon? Type 'once in a blue moon' into Google's search bar and you'll get '1.16699016 10-8 hertz', or about 2.715 years.