May the 4th be with you！

While many of you may be familiar with this pun-loaded greeting from the Star Wars, Chinese people, especially the youth, have their own special celebration on the day.

May (the) Fourth  n. (also 4 May, etc.) Chinese History (attributive) designating or relating to a demonstration held by students in Peking (Beijing) on 4 May 1919 to protest against the Chinese government’s failure to oppose the decision by the Versailles Peace Committee to allocate Germany’s former possessions in China to Japan; (also) designating the wider cultural and intellectual revolution in China for which this demonstration is generally regarded as having been a catalyst; esp. in May (the) Fourth Movement.

Oxford English Dictionary