Dec. 8 marks the Feast of the Immaculate Conception in the Catholic liturgical calendar. In 2013, the holy day will be observed on Dec. 9 in many parishes. Catholics believe that the Blessed Virgin Mary was preserved from original sin so that she could birth the Messiah, Jesus and honor her on this day. Here are activities for parents and children to celebrate the Feast of the Immaculate Conception and Advent, a Christmas preparatory season during which the feast falls. Feast of the Immaculate Conception, Advent Activities for Parents and Children