This day is historically England's name for St Stephen's Day - St. Stephen was one of the first Christian martyrs, being stoned to death in Jerusalem around A.D. 34-35 - the 26th December, which is a public holiday in most countries in Europe and many countries around the world with predominantly Christian populations. In the Eastern Orthodox Church, St Stephen's Day is celebrated on the 27th of December, although in Greece the Greek Boxing Day (Synaxis Theotokou, Σύναξις Θεοτόκου) is also celebrated as a public holiday on the 26th of December and is not related to the English version.
In Ireland the Bank Holidays Act 1871 established the feast day of St. Stephen's Day as a non-moveable public holiday on December the 26th, although since partition the name "Boxing Day" is used by the authorities in Northern Ireland and it has become a moveable public holiday in line with the rest of the UK. The Banking and Financial Dealings Act of 1971 established "Boxing Day" as a public holiday in Scotland. In the Australian state of South Australia, December the 26th is a public holiday known as Proclamation Day.
It is usually celebrated on the 26th of December, the day after Christmas Day; however, unlike St Stephen's Day, Boxing Day is not always on the 26th of December, its associated public holiday can be moved to the next weekday if the 26th of December is a Saturday or Sunday. The movement of Boxing Day varies between countries.
Boxing Day dates back to past centuries when it was the custom for the wealthy to give gifts to employees or to people in a lower social class, most especially to household servants and other service personnel. The name has numerous folk etymologies.
As with Christmas itself, some elements of Boxing Day are also likely related to, and ultimately derived from, the ancient Roman Saturnalia, which also had elements of gift giving and social role reversal.
In the countries that observe this holiday, 26 December is commonly referred to as Boxing Day, no matter what day of the week it occurs. However, in some countries, fixed-date holidays falling on Saturday or Sunday are often observed on the next weekday. Technically, Boxing Day cannot be on a Sunday - that day being the officially recognized day of worship, so traditionally it was the next working day of the week following Christmas Day, (i.e. any day from Monday to Saturday). In recent times this tradition has been either forgotten or ignored, and 26 December is considered by most to be Boxing Day when it falls on a Sunday. 1993 was the last year when 26 December was called Christmas Sunday in the UK; in 1999, the next time the date fell on a Sunday, it was Boxing Day.
If Boxing Day falls on a Saturday, then Monday 28 December is declared a public holiday. In the United Kingdom and some other countries this is accomplished by Royal Proclamation. In some Canadian provinces, Boxing Day is a statutory holiday and is always celebrated on 26 December. As with most statutory holidays in Canada if it falls on a Saturday or Sunday, compensation days are given in the following week.
If Boxing Day falls on a Sunday, then in countries where it is a public holiday the Statutory Holiday is moved to Monday 27 December. In that event, Christmas Day would be on a Saturday, so Tuesday 28 December would be declared a holiday in lieu, that being the next available working day - thus the Boxing Day holiday occurs before the substitute Christmas holiday.
If Christmas Day falls on a Sunday, then Boxing Day is on Monday 26 December, and no Royal Proclamation is required. In such a circumstance, a 'substitute bank holiday in lieu of Christmas Day' is declared for Tuesday 27 December; again with the Boxing Day holiday occurring before the substitute Christmas holiday.
Although the same legislation—the Bank Holidays Act 1871—originally established the Bank Holidays throughout the United Kingdom, the holiday after Christmas was defined as Boxing Day in England and Wales, and the feast day of St. Stephen's Day in Ireland.
In Australia and Canada, Boxing Day is primarily known as a shopping holiday, and a time where stores have sales, often with dramatic price decreases. For many merchants, it has become the day of the year with the greatest revenue. In recent years, this has been expanded to "Boxing Week". While Boxing Day is actually on 26 December, many retailers who hold Boxing Day Sales will run the sales for several days before or after 26 December, often up to New Year's Eve.
In some areas of Canada, particularly in Atlantic Canada and parts of Northern Ontario, most retailers are prohibited by law from opening on Boxing Day. In these cases, any sales specifically scheduled for December 26 are moved to the 27th.
--Wizard's Note: And I thought it was the day that all the empty Christmas Boxes were tossed to the curb!