The Advent Calendar traces its origins to 19th Century Germany, where it was used by Lutherans to encourage children to count down the days to Christmas. Generally it consisted of a paper picture, often of a religious theme, with 24 doors. Each door concealed a picture or a Bible verse or (usually very bad) candy. As Christmas approached, the doors usually became larger and more central, and the prizes grew in value. There is no data available about the number of Advent Calendars that are started and never finished, or creating candy feasts of missed weeks.
Most ironically, the Advent Calendar is almost never a calendar of Advent, which begins 4 Sundays before Christmas however the calendar falls (of course these blog posts also follow the calendar of December and not the Church calendar.
Most Advent Calendars are secular now as the tradition has been embraced by parents of all sorts, trying to find creative ways to teach children to wait through the months.
There are also some weird Advent Calendars
Asa always, I welcome your comments.