Ice Age: A Mammoth Christmas is a 2011 computer animated television special and part of the "Ice Age" franchise, produced by Blue Sky Studios and directed by Karen Disher. It premiered on November 24, 2011 on Fox in the United States and in the United Kingdom at christmas on Channel 4 and E4 and it was released two days later to DVD and Blu-ray.
Ice Age: A Mammoth Christmas was shown in December on Fox.
It said that it premiered in November, but they may have shown an encore in December. There is no way to know. 
( z1 show :ARG1 ( z2 broadcast-program :name ( z3 name :op "Ice" :op "Age" :op "A" :op "Mammoth" :op "Christmas" ) ) :time ( z4 date-entity :month 12 ) :medium ( z5 broadcast-program :name ( z6 name :op "Fox" ) ) )