Boxing Day is always celebrated on December 26th or the day after December 25th, Christmas Day. It is a holiday used to get rid of the boxes from Christmas and calendar to others.
This is a national holiday that most have the day off for. Germans celebrate with a feast and giving small gifts to one another recycling the boxes that were used at Christmas.
Boxing Day comes from the tradition of elite British households giving their servants their leftover boxes from Christmas to which the servants would use these to give small gifts to each other. Many also use it to celebrate St. Stephen as well as boxing day.