A German printer named Gerhard Lang is credited with the idea of the Advent Calendar itself. 
He designed cardboard Advent calendars around the turn of the century and later in the 1920s, 
came up with the idea of cutting out little doors that could be opened each day. 
Behind each door, one could expect to find a devotional picture or Bible verse.

For those who are not religious, modern Advent calendars are a treat-filled way of marking off the days leading up to Christmas or Santa's arrival. 

Have a great weekend