If you like to write the date with the month first and then the day, then it's Pi Day for you.
March 14 = 3.14 = pi = π
And even if you write the day first, and then the month, you can still celebrate Pi Day with the rest of geekdom.
Pi is the ratio between the diameter of a circle and its circumference. Remember that from your school days?
You can celebrate Pi Day by calculating the circumference of a circle, committing Pi to memory (this is how to do it), or just by eating pie.
I prefer the latter.
Pictures borrowed from the internet, no I didn't make that pi pie, I wish I had. Maybe next year, if I remember....