The origins of this Christmas tradition come from the German Lutherans, as early as the beginning of the 19th century. The calendar started off simple, a written way to count down the days until Christmas. Eventually, lighting 24 candles became popular.
Very early in the 20th century, Gerhard Lang
was credited with printing the first Advent calendar. Several years
later, he decided to add little doors that would open to reveal the
date or a scripture. It wasn't’t until after WWII that the calendars
began to be filled with candies and treats for the days before