A little history about the Second Day of Christmas(collected from Wikipedia).
St. Stephen's Day
St. Stephen's Day, or the Feast of St. Stephen, is a Christian saint's day to commemorate Saint Stephen, celebrated on 26 December in the Western Church and 27 December in the Eastern Church. Many Eastern Orthodox churches adhere to the Julian calendar and mark St. Stephen's Day on 27 December according to that calendar, which places it on 9 January of the Gregorian calendar used in secular contexts. It commemorates St. Stephen, the first Christian martyr or protomartyr.
It is an official public holiday in Alsace, Austria, Balearic Islands, Bosnia and Herzegovina, Catalonia, Croatia, Czech Republic, Denmark, Estonia, Finland, Germany, Ireland, Italy, Luxembourg, Macedonia, Montenegro, Moselle, Norway, Philippines, Poland, Romania, Serbia, Slovakia and Sweden. The date is also a public holiday in those countries that celebrate Boxing Day on the day instead/as well, such as Canada.
Boxing Day
Boxing Day is traditionally the day following Christmas Day, when servants and tradesmen would receive gifts from their bosses[1] or employers, known as a "Christmas box". Today, Boxing Day is habitually known as the bank holiday that occurs on 26 December. It is observed in the United Kingdom, Canada, Hong Kong, Australia, New Zealand, South Africa and some other Commonwealth nations.