Encode the date in Christmas Eve format
SmileBASIC, 73 71 67 bytes
?&quot;Christmas&quot;;
@L?&quot; Eve&quot;*(D!=P);
P=D
DTREAD OUT,M,D
IF M/D-.48GOTO@L

The program prints &quot;Christmas&quot;, then prints &quot; Eve&quot; every time a day passes, until it is December 25th. (12/25 = 0.48)
May take up to a year to run.