Dec 25 vs Christmas Day

Dec 25 and Christmas Day both are nouns.

Word	Noun	Adjective	Verb	Adverb
Dec 25	Yes	No	No	No
Christmas Day	Yes	No	No	No

As nouns, Dec 25 and Christmas Day are synonyms defined as:

Dec 25 and Christmas Day: a Christian holiday celebrating the birth of Christ; a quarter day in England, Wales, and Ireland

Other synonyms of Dec 25 include Christmas, Xmas.

Dec 25 (noun)	Christmas Day (noun)
a Christian holiday celebrating the birth of Christ; a quarter day in England, Wales, and Ireland	a Christian holiday celebrating the birth of Christ; a quarter day in England, Wales, and Ireland