If you go back far enough, nearly all formats switched to Christmas music from Christmas Eve to, as you said, noon on Christmas Day, or maybe even 10 a.m. I remember Top 40 stations and Talk stations even did it. Partially this was to give the regular staff off on Christmas Eve and Christmas morning. You could suspend your regular format and just have a board op run Christmas music from 6 p.m. on Dec. 24 to 10 a.m. or noon on Dec. 25.
But these days, not as many stations do this. Talk stations just run repeats of recent talk shows. Top 40, Country, Urban AC and Hot AC stations sprinkle a few Christmas songs into their regular format. The staff is off anyway. Music formats can just automate or voice track. You don't need to suspend the format with a board op playing Christmas songs.
And by the way, we really shouldn't title a post "Just Wondering" or "Sorta Surprised." We should know what the post is about from the title. Then we can decide whether to click it or not. Maybe you wanted to say "Christmas Music Keeps Playing Until Midnight?" or something like that.