Star Wars Day is an unofficial holiday in May created by fans to honor the Star Wars franchise created by George Lucas. Observance of the holiday spread quickly due to Internet, social media, and grassroots celebrations. The date was chosen as “May the 4th” due to its sounding similar to the series’ phrase “May the Force be with you” in which fans commonly say “May the fourth be with you”.
The reference was first used on May 4, 1979, the day Margaret Thatcher took office as Prime Minister of the United Kingdom. Thatcher’s political party, the Conservatives, placed a congratulatory advertisement in The London Evening News that stated “May the Fourth Be with You, Maggie. Congratulations.” This reading of the line has also been recorded in the UK Parliament’s Hansard.
In 2011, the first organized celebration of Star Wars Day took place in Toronto, Ontario, Canada at the Toronto Underground Cinema. Produced by Sean Ward and Alice Quinn, festivities included an Original Trilogy Trivia Game Show; a costume contest with celebrity judges; and the web’s best tribute films, mash-ups, parodies, and remixes on the big screen. The second annual edition took place on Friday, May 4, 2012.
Fans (even government officials) have celebrated Star Wars in a variety of ways in social media and on television.
Minor League baseball teams such as the Toledo Mud Hens and the Durham Bulls have worn special uniforms as part of “Star Wars Day” promotions.
(source: Wikipedia – http://en.wikipedia.org/wiki/Star_Wars_Day )