November 27, 1095 - Pope Urban II declares the First Crusade at the Council of Clermont.
The first entry at Wiki.
September 11, 1683: Siege of Vienna lifted.
http://gatesofvienna.blogspot.com/2006/09/other-september-11th.html
WTH?
http://www.freerepublic.com/focus/f-news/2138628/posts
Seems there’s a trend.