National Cocoa Day
National Cocoa Day falls on December 13, and a single Dutch press patented in 1828 is the reason cocoa is cheap, mixable and everywhere.
December 13
3 holidays
Violin Day
Violin Day falls on December 13, honoring an instrument barely changed in four centuries, and blind tests have unsettled what everyone assumed about the old ones.
Choral Day
Choral Day falls on December 11, and singing together turns out to synchronize the bodies of the people doing it, which is measurable rather than metaphorical.