Wikipedia holidays or the Order of the Day is a Wikipedia award bestowed honoris causa by Jimmy "Jimbo" Wales, co-founder of Wikipedia, typically to a Wikimedia developer for exceptional service to the community. Its motto is "We make the Internet not suck", derived from an interview with the founder. Since its founding in 2001, the total number of inductees include five persons.

Here is the list of Wikipedia holidays.

January 15 since 2001: Wikipedia Day, the day Wikipedia went public (not actually proclaimed by Jimbo, just universally acknowledged by the Wikipedia community).

January 25 since 2002: Magnus Manske Day, "when Wikipedia switched to the Phase II software, the precursor to MediaWiki".

October 31 since 2003: Tim Starling Day, for "the new parsing algorithm".

June 1 since 2004: Brion Vibber Day, for "his incredible dedication and hard work, without which the project should have collapsed a long time ago".

April 20 since 2012: Justin Knapp Day, to "the first person to ever make 1,000,000 edits".

More Info: en.wikipedia.org