It is to me though. I seem to have several friends with birthdays tomorrow who all are well aware of that anniversary so I've often been told about it. I guess it was a very significant date at one time.
Interesting question though. Erm, 9/11 is probably one of them. Not least because we actually call the day by it's date rather than the event. 25th December is quite famous... Can't remember why though.
For me 11th August 2011 is an important one as it was my wedding day. Ah sweet. Mind you, if you ask Peter he'll say 10th August 2012 or some other answer that's kind of close but not quite there. Hehe!