From Academic Kids
There is much dispute over the true origins of Boxing Day, but one common story of the holiday's origins is that servants used to receive Christmas gifts from their employers on the first weekday after Christmas, the day after the family celebrations. These were generally called their Christmas boxes. Another story is that this is the day that priests broke open the collection boxes and distributed the money to the poor.
There is some debate as to whether Boxing Day is always December 26, as opposed to the first weekday after Christmas Day. In modern popular usage, "Boxing Day" always means December 26. When Boxing Day falls on a Sunday, some Christians choose to celebrate it on 27 December in order to avoid a clash with the Christian sabbath. In any case, in Commonwealth countries, fixed-date holidays falling on Saturday or Sunday are observed on the next weekday. It is noteworthy that in the government holiday listings (http://www.dti.gov.uk/er/bankhol.htm) of the United Kingdom for 2004, the public holiday in lieu of Boxing Day was observed on Monday 27 December, before the holiday in lieu of Christmas Day on Tuesday 28 December.
Boxing Day in the UK is traditionally a day of sport, usually football and horseracing. In Canada, Boxing Day is also observed as a public holiday, and is a day when stores sell their excess Christmas inventory at significantly reduced prices. Boxing Day has become so important for retailers that they often extend it into a Boxing Week. This occurs similarly in Australia and New Zealand. In Australia, the cricket test match starting on December 26 is called the Boxing Day Test Match, and is played at the Melbourne Cricket Ground before the largest crowd of the summer. In Sydney, the annual Sydney-Hobart Yacht Race, one of the biggest and most prestigious ocean racing events in the world, begins on this day, as the yachts depart Sydney Harbour before many thousands of spectators around the harbour and in spectator boats. In South Africa the 26th is also observed as a public holiday. Although officially the day is known as the Day of Goodwill, it is also often referred to as Boxing Day by local English speakers. It is common for a cricket test match, played against a visiting international team, to start on this day.
In Germany, Denmark, Sweden, and the Netherlands, the 26th is known as the second day of Christmas ("der zweite Weihnachtsfeiertag" or Stefanitag in Austria) and is also a public holiday. In Ireland, the holiday is known as St Stephen's Day, or Wren's Day; in Wales, it is known as Gŵyl San Steffan (St Stephen's Holiday). In Catalonia, this day is known as Sant Esteve, Catalan for St Stephen.