These days the word "Advent" mostly comes before the world "calendar" - but it has a meaning deeper than novelty-shaped chocolates behind cardboard doors.
Advent is derived from the Latin Adventus means "coming", and was originally a period of fasting - a far cry from indulging in everything from a luxury chocolate to a gin miniature a day, depending on what fills your Advent calendar.
It doesn't start on December 1 - or at least, not always
December 1 may be the first door on your Advent calendar, but Advent doesn't start until Sunday December 3 this year - though it can also start in November.
Like Easter and Lent, the date for Advent is flexible. It begins on the fourth Sunday before Christmas, Advent Sunday, and is a time when Christian churches remember the anticipation of the people of Israel awaiting the prophesied coming of the Messiah.
Advent crowns existed before Blue Peter
Many churches, and families, commemorate Advent with a wreath (or crown) of four candles - lighting the first one on Advent Sunday, and another for each Sunday leading up to Christmas.
Often a final candle is lit in the centre of the wreath on Christmas morning to represent Jesus, The Light of the World.