Available at ChristmasVacationCollectibles.com
In National Lampoon’s Christmas Vacation an advent house calendar is used to show the passage of time.
An advent house is a calendar that counts down the 24 days from December 1st to December 24th, Christmas Eve. On December 1st the tower and atrium are lit. On each of the following days a new window or door is opened to reveal a Christmas scene. Though a common misconception there is no door for Christmas itself.