What are you doing today, March 14, at 1:59 p.m.? Celebrating irrational numbers, we hope -- that's when the Exploratorium, San Francisco's science museum, will be kicking off their 18th Annual Pi Day party.

Because pi is all about circles, participants will learn how to make pizzas -- and because scientists love bad puns, a certain type of round baked good with a crusty top will also be served (donated by Bakers Square.) At 1 p.m., the sixth graders of Oakland's Kipp Bridge College Prep will sing a pi song, and then at 1:59, there's a pi-rade that goes around the round museum rotunda 3.14 times, while everyone sings happy birthday to Albert Einstein. (Today is Albert Einstein's birthday too, apparently. It's also Billy Crystal's birthday, but no one's singing happy pi day songs to him.)

If you can't make it out to the Exploratorium, you can celebrate pi day privately -- check out these pi songs. And if you've got other commitments today, don't fret -- you can celebrate "Pi Approximation Day" on 22/7, if you write your dates in international format.