As you get older you begin to appreciate this day more than Christmas because there’s no work involved in preparing anything. Sleeping in followed by sampling all the leftovers. Some of the history of Boxing Day (also known as St Stephens Day) here and here:

The custom arose because servants, who would have to wait on their masters on Christmas Day, had the next day off. They were given gifts from their masters and would go home to visit their families. In the church, the money in the Alms (charity) boxes was given to the poor. The church parishioners deposited donations into a box the clergyman put out for that purpose and handed it out at Christmas.