Boxing Day is a holiday celebrated the day after Christmas Day, thus being the second day of Christmastide. It originated in the United Kingdom and is celebrated in a number of countries that previously formed part of the British Empire. Boxing Day is on 26 December, although the attached bank holiday or public holiday may take place either on that day or one or two days later.

In the UK, 26 December (unless it is a Sunday) has been a bank holiday since 1871. When 26 December fell on a Sunday,27 December would have been a Bank Holiday. When 26 December falls on a Saturday, the public holiday is on the following Monday. If 26 December falls on a Sunday, the public holiday is the following Tuesday.

In the UK, Canada, Australia, Trinidad and Tobago, and New Zealand, Boxing Day is primarily known as a shopping holiday.

From Wikipedia