If you are on Facebook, here is the event link.
For those that aren't, here are the copy pasted rules.
"March 1st is Derpy Day!
Be sure to remember the observances of this most Pony of Hoofidays.
-Muffins. At least one must be consumed by days end, lest Pinkie's tail twitch for you.
-The Muffin shaped cake is fine even if you are not Orthodox Derpy.
-An article must be moved from one area of the house and placed in the wrong one for the entire Hoofiday.
-Letters must be hoof written and delivered to those you love within delivery distance. E-mails have now been recognized for those too far for this observance.
At least try to deliver one RL letter.
The Letters are to be about why you love them or are thankful they are your friend. (Bonus writing a loving friendship letter to an enemy.)
-Anytime a picture of you is taken or you see yourself in a mirror, you must give the traditional Derpy Occular salute. 9_6
Be well and Happy DERPY DAY!"