The origins of the Advent calendar come from German Lutherans who, at least as early as the beginning of the 19th century, would count 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 1930's. In this same time period, Sankt Johannis Printing Company started producing religious Advent calendars, with Bible verses instead of pictures behind the doors.
The practice disappeared during World War II, apparently to save paper. After the war, Richard Sellmer of Stuttgart resurrected the commercial Advent calendar and is responsible for its widespread popularity. His company, Richard Sellmer Verlag, today maintains a stock of over 1,000,000 calendars.
The traditional calendar consists of two pieces of cardboard on top of each other. Twenty four doors are cut out in the top layer, with one door being opened every day, from December 1 to December 24 (Christmas Eve). Each compartment can either show a part of the Nativity story and the birth of Jesus, or can simply display a piece of paraphernalia to do with Christmas (e.g. Bells, holly). Advent Calendars can also consist of cloth sheets with small pockets to be filled with candy or other small items. Many calendars have been adapted by merchandisers and manufacturers to include a piece of chocolate or a sweet behind each compartment, aimed at children. These have often been criticised for not relating to the Nativity and simply cashing in on Christmas sales. These are aimed at small children who are counting down to Christmas, because that is when Santa Claus comes.
The number of doors can also increase to twenty five or twenty six to cover Christmas Day, Hanukkah and Boxing Day, and further to thirty one or thirty two to include New Year's Eve and New Year's Day. This latter act was particularly evident over December 1999, counting down to January 1, 2000 and what was largely perceived as the start of the third millennium (although the same thing did not happen a year later in the lead up to what was technically the real third millennium on January 1, 2001).
The Advent calendar is normally of standard dimensions, but can be found in other shapes, such as a model of a house. There are alternative forms of Advent calendar, such as those made from felt or other material, or a chain of candles that can be lit day by day. The German city of Dresden has a giant calendar built into a fairytale castle on its Christmas market, the Striezelmarkt. Nowadays there are also digital Advent calendars.