I can't speak to whether or not this is an established tradition, but I can tell you that I have a good friend who is currently a 4th year, and she received her acceptance call from the dean on New Year's Eve (during the daytime hours, of course). She was accepted during the 05-06 application cycle for fall 2006 matriculation. Beyond that I don't know, but wouldn't that be the greatest Christmas present ever?! (Cornell is my IS.)