There's no reason why articles or announcements in newspapers or on radio that are designed to coincide with Christmas eve or day shouldn't be called "Christmas". For example, "How to cope with last minute holiday gifts" slights Christmas if it comes on December 24th or 25th, days everyone knows are Christmas days. Let them know they are responsible for knowing what day it is. If they know there's a holiday, they can just as easily say which holiday. Tell them you don't buy gifts or do anything else in the name of "holiday" on Christmas eve or day.