The exact origin of Pi Day (observed) is unknown but most historians believe it comes from the ancient Mesopotamians who incorrectly believed pi was an irrational number, approximately 3.14. Other's (hardcore gaming freaks) believe that 314 was the score that Mario got for killing a Galapagos Island Turtle As science has proven pi equals exactly 3.0 (which has given rise to the belief that this was a major cause of the fall of Mesopotamia, but that is another subject entirely). Today Pi Day (observed) continues to be celebrated on March 3.14th simply because there is no March 0.
However, many believe that Pi Day should be held at midnight 31st dec-1st jan, simply because, for this minute, the date is 0.
Many also believe that Pi day should be celebrated by eating kittens and quoting Oscar Wilde, simply because both activities are awesome. Also, on Pi Day it is legal to kill a man in the US. (see below)
edit Pi Day in various places
In the USA, Pi Day is celebrated by mathematicians and bakery chefs in general, because they have nothing better to do. To celebrate, they eat kittens, quote Oscar Wilde, make pies, and kill men. On January 19th, 1264 the so-called "Pi Act" was passed by the -346th Congress, enabling legal massacres.
On Pi Day, Bakery chefs and mathematicians grow powers half close to those of Chuck Norris and become invincible to everything but I Can't Believe It's Not Hitler
In New Zealand, Pi Day is celebrated because it creates a day off for the hardworking mathematicians.
In Australia, Pi Day is celebrated by slaughtering three Sheep.In England, Pi Day is celebrated by...well...we dont.
In Soviet Russia, Pi Day Celebrate YOU!!
edit Why does Pi Day exist?
The only current answer for this is: Because it does. Mathematicians and Historians are working together to work this out, but thus far the research has yielded no results. We hope that there will be some results in the near future.
edit Pi Day-It's Future
Of the United Mathematic Nation Committie (UMNC), all 12 agree it should be a worldwide holiday, not in some country where they may have made it up. Oscar Wilde, Soviet Russians and the United States of America (The Worlds Leading Mathematic Wonders) decided that people should memorise Pi to it's 314th decimal place, or they shall be manufactured in a box of Uncyclopedios or Shepereds Pie.