[dragonwriter]

No, Advent is the liturgical season preceding Christmas, beginning the fourth Sunday before Christmas (which is also the Sunday nearest November 30), it is a period of at least three weeks and one day (the shortest period that can start on a Sunday and include four Sundays.)

The 12 days of Christmas start on Christmas and end on January 5, the eve of the Feast of Epiphany.

12-day advent calendars are a fairly recent invention that mirrors the 12-days of Christmas, but has no direct correspondence to anything in any traditional Christian religious calendar (the more common 24-day format is also a modern, but less recent, invention detached from the religious calendar, that simplifies by ignoring the floating start date of advent and always starting on Dec. 1.)

[wang_li]

In the Orthodox Church advent starts on November 15th and continues until December 24th.

[dragonwriter]

True, I should have specified that the timing I was providing was the Western tradition; the Orthodox (both Eastern and Oriental, I believe) tradition has a 40-day Nativity Fast (in some, the name is different in others) mirroring the 40-day season of Lent, that is similar (in terms of being a preparatory season for the Feast of the Nativity) to the Western Advent.