How to play
The time signature is 6/4.
Each chord in this transcription has the same duration - one third of a bar, or 2/4. Keep in mind the different rhythm patterns explained below.
This rhythm pattern goes throughout the song; / and . stand for stressed and unstressed beats, respectively:
 |1   2   3   4   5   6  |
 |/ . / . . / . / . / . .| - chords (5 out of 12 beats in a bar)
 |/ . . . / . . . / . . .| - bass (3 out of 12 beats)
You've got to combine these two together, if you're playing one guitar.
 
Wikipedia: http://en.wikipedia.org/wiki/Christmas_Time_Is_Here
The story of how the lyrics were written: http://impressionsofvince.blogspot.ru/2012/10/lee-mendelson-lyricist.html
The song has been performed by many artists. This transcription is for the performance of Michael Franks and David Benoit: