The origins of the Advent calendar come from German Lutherans who, at least as early as the beginning of the 19th century, would count down from 24 to the days of Advent physically. Often this meant simply drawing a chalk line on the door each day, beginning on December 1. Some families had more elaborate means of marking the days, such as lighting a new candle (perhaps the genesis of today's Advent wreath) or hanging a little religious picture on the wall each day.
The 24 candles might also be placed on a structure, which was known as an "Advent clock". In December, 1839, the first verifiable public Advent wreath was hung in the prayer hall of the Rauhes Haus (relief house) in Hamburg, although it had been a family practice in parts of German-speaking Europe since the 17th century.
The first known Advent calendar was handmade in 1851. According to the Austrian (NÖ) Landesmuseum, the first printed Advent calendar was produced in Hamburg in 1902 or 1903. Other authorities state that a Swabian parishioner, Gerhard Lang, was responsible for the first printed calendar in 1908.
Lang was certainly the progenitor of today's calendar. He was a printer in the firm Reichhold & Lang of Munich who, in 1908, made 24 little colored pictures that could be affixed to a piece of cardboard. Several years later, he introduced a calendar with 24 little doors. He created and marketed at least 30 designs before his firm went out of business in the 1930s. In this same time period, Sankt Johannis Printing Company started producing religious Advent calendars, with Bible verses instead of pictures behind the doors.