Is the time 5:15pm a reference back to the very first episode for the 50th Year?  Probably not.

This years annual Doctor Who Special, called The Snowmen, Will officially air on Christmas Day, at 5:15pm on BBC One. 

The earlier time of 5:15pm could be mainly be due to the time clash avoidance between Call the Midwife on BBC One and Downtown Abbey on ITV1. You can see the full BBC One Christmas Day Evening schedule below:
3:10pm: Shrek Forever After
4:35pm: Room on the Broom
5:00pm: News & Weather
5:15pm: Doctor Who
6:15pm: Strictly Come Dancing
7:30pm: Call the Midwife
8:45pm: Eastenders
9:45pm: The Royle Family

Remember to pick up the traditional Radio Times Double Christmas Issue to see all the listings! Out Wednesday 12th December 2012.