Actually, the traditional date has a stronger claim than skeptics like to admit. This article is worth a read:
http://www.touchstonemag.com/archives/article.php?id=16-10-012-v
for home
Excellent article. The early Church believed that March 25th was a most important day.
http://www.newadvent.org/cathen/01542a.htm
"[T]he ancient martyrologies assign to the 25th of March the creation of Adam and the crucifixion of Our Lord; also, the fall of Lucifer, the passing of Israel through the Red Sea and the immolation of Isaac."
It really ought to be restored as a Holy Day of Obligation.