Its Wikipedia 15th Birthday :: January 15, 2001.

January | Friday | 15, 2016 :: January 15 is known as Wikipedia Day to Wikipedians. On this date in the year 2001, the wiki-based Wikipedia project went public after spending five days on Nupedia.

Wikipedia Day has been celebrated, both online and offline, for several years. In 2011 there was a big worldwide celebration of Wikipedia 10, and this tradition continued with diverse local meetups and wiki-events for Wikipedia Day on Sunday 15 January 2012.

Wish you a very Happy Birthday Wikipedia.