International work-related curiosity

Since this is the first year I've been closely involved in the long-standing British tradition of special Christmas stamps (this year's designs), I've been curious to know whether this is a unique thing.

Are there special Christmas stamps where you live? Do people send calendars (this seems to be a tradition among a significant number of British people, but not one I'd actually come across before I started working for a shop that sold them)?

Are there other traditions connected with posting for Christmas?