Saint Stephen's Day, December 26, honors Saint Stephen — the first Christian martyr. It is widely observed across Catholic and Orthodox Europe (often as a continuation of Christmas) and corresponds to Boxing Day in Anglo-Saxon countries.
Stephen, stoned to death around 34 CE for his preaching, is celebrated as the first martyr of the early Christian church (proto-martyr). His feast was established by the 4th century.
In Ireland: "Wren Day" — traditionally young men in costume carry a hunted wren around villages collecting money. Today the wren is symbolic. In Italy: continued Christmas family meals. Eastern Europe: church services and family time.
Leftover Christmas roast. In Ireland, traditional Christmas pudding.
Public holiday in Ireland, Italy, Germany, Austria, Switzerland, Croatia, Poland, Czech Republic, Hungary, Romania, Serbia, Catalonia. Boxing Day in UK and Commonwealth.