Day after Christmas or Boxing Day was started in the UK about 800 years ago, during the Middle Ages. It is a holiday celebrated on the day following Christmas Day, when servants and tradesmen would traditionally receive gifts known as a "Christmas box" from their masters, employers or customers, in the United Kingdom and Commonwealth nations. Boxing Day as a bank holiday or public holiday takes place on 26 or 27 December.
This days off for most workers where it’s a state holiday. In places where it’s not a public holiday, most families use up a vacation day, as most schools are closed.
In the liturgical calendar of Western Christianity, Boxing Day is the second day of Christmastide, and also St. Stephen’s Day. In USA it is a holiday in North Carolina, Oklahoma, South Carolina, Texas, U.S. Virgin Islands. In some European countries, notably Germany, Poland, the Netherlands and Scandinavia, 26 December is celebrated as a Second Christmas Day.
Source: whychristmas.com | wikipedia.org