Merry Atavus Day

It would be nice if chatting with any humanoid creature, be it peaceful or hostile, during December 24th and 25th had a small chance of resulting in the line "Merry Atavus Day!" instead of the usual message.

The in-game day? Or the real-world day? Because if the latter, then Atavus Day would last several in-game days... perhaps Atavus has a whole week?

As long as it takes for one of the farmers to cut the Grand Atavus Day Stollen without dropping the knife.