The calendar's 3D "windows" will be opened every night
The huge calendar, which has been hung from scaffolding on the city's town hall, was unveiled to the public for the first time on Friday.
Representatives from the Guinness Book of Records were on hand to verify its place in history.
The calendar measures 55 metres wide and 15 metres high and its special 3D "windows" will be opened at 1800 GMT every day leading up to Christmas Eve.
'Traditional and seasonal'
However the contents of the windows are being kept secret.
Drinks company Coca Cola are sponsoring the calendar which features the company's famous Coca-Cola Santa, whose image is 70-years-old this year.
Company spokesman Andrew Coker said: "The calendar is very traditional, very seasonal and the biggest in the entire world."
Birmingham City Council said it hoped the calendar would be another boost to Christmas shopping in the city.
Council leader Albert Bore said: "This is an exciting project taking place in the very heart of Birmingham.
'Huge success'
"It will provide visitors to the city with a superb visual reminder of the festive season and hopefully attract more shoppers to the city centre."
He added: "We have worked hard with Coca-Cola on this project and I'm confident it will be a huge success."
The Advent calendar tradition has its origins in the 19th Century from the protestant area of Germany.
Protestant Christian families made a chalk line for every day in December until Christmas Eve.
In the early 20th Century the chalk lines were replaced with printed calendars.
The first printed specimen is credited to Gerhard Lang (1881-1974) from Maulbronn in Germany.
Advent marks the start of the Christmas season. It begins on the Sunday nearest 30 November, the feast day of St. Andrew the Apostle, and covers four Sundays.