Stack Overflow, Server Fault, Super User and Meta all launched on different days, does anyone know the dates exactly?
Stack Overflow: September 15, 2008 for Public Beta.
Server Fault: May 26, 2009 for Public Beta.
Super User: July 14, 2009 for Semi-Private beta, August 18, 2009 for full launch
Meta: Some time between SF and SU Beta.
SO and SF had a private beta before and launched a month or so after, couldn't find the exact dates right now.