In Britain, Boxing Day is usually celebrated on December 26th, which is the following day after Christmas Day. However, strictly speaking. Boxing Day is the first weekday after Christmas. Like Christmas Day. Boxing Day sing a public holiday. This means it's a non-working day in the whole of Britain. When Boxing Day falls on a Saturday or Sunday, the following Monday is the public holiday.
The exact origin(起源)of the holiday is unclear. One of the thoughts is that during the Middle Ages, when great sailing ships were setting off to discover new land, a Christmas Box was placed by a priest (神父)on each ship. Those sailors who wanted to ensure a safe return would drop money into the box. It was sealed up and kept on board until the ship came home safely. Then the box was handed over to the priest in the exchange for the saying of a Mass of thanks for the success of the sailing. The priest wouldn't open it to share the contents with the poor until Christmas.
One more thought is about the “Alms Box” placed in every church on Christmas Day. Worshippers (做礼拜的人)put gifts for the poor into it. These boxes were always opened the day after Christmas, that is why that day became know as Boxing Day.
Today, many businesses, organizations and families try to keep the traditional spirit of Boxing Day alive by donating(捐赠)their time, services and money to aid Food Banks, providing gifts for the poor, or helping families in need. Besides, spending time with family and shopping are popular Boxing Day activities now.