Saturnalia

Today, ante diem xvi kalendas januarias, is the 1st day of the ancient pagan Roman celebration of Saturnalia. 

Saturnalia was a festival in honour of Saturn.  There were banquets and people wore a soft floppy hat called a pileus.

No business could be conducted, so all the shops and markets were closed.  People would gamble, eat a lot and exchange gifts.  One custom was that masters would serve their slaves.