Christmas Tree Advent Calendar by Pockets of Learning is a holiday favorite with many families now enjoying it into the second generation! Help your family create special holiday memories with this festive advent countdown calendar. This heirloom piece is our most popular request for the holiday season. Each of the 24 pockets contains a decorative ornament that attaches onto the tree. Put one ornament on the tree each day starting on December 1. Replacement pieces are available.