"Yuri's Night" is a celebration of two events: (1) the first successful launch of a human in space (Yuri Gagarin) on April 12, 1961, and (2) the first launch of a U.S. space shuttle on April 12, 1981. It is a celebration of all past, present, and future human efforts in space exploration.
Further information on Yuri's night-Yuri's night blog
Yuri Gagarin on Wikipedia
A video from the Spanish TV (RTVE) about the first spaceflights.
