The Feast of the Immaculate Conception takes place on December 08, 2015 in the Catholic Church. It is celebrated nine months before the feast of the Nativity of Mary, which is celebrated on September 8. The Immaculate Conception is a dogma maintaining that from the moment when she was conceived the Blessed Virgin Mary was kept free of original sin and was filled with the sanctifying grace normally conferred during baptism.
The Feast of the Immaculate Conception is observed in many Catholic countries as a holy day of obligation or patronal feast, and in some as a national public holiday. The feast is often celebrated with Holy Mass, parades, fireworks, processions, ethnic foods, and cultural festivities in honor of the Blessed Virgin Mary and is generally considered a "family day", especially in many Catholic countries.
The doctrine of the immaculate conception is not to be confused with her virginal conception of her son Jesus. This misunderstanding of the term immaculate conception is frequently met in the mass media. Catholics believe that Mary was not the product of a virginal conception herself but was the daughter of a human father and mother, traditionally known by the names of Saint Joachim and Saint Anne.
The Church celebrates the Feast of the Immaculate exactly nine months before celebrating the Nativity of Mary. The feast of the Annunciation (which commemorates the virginal conception and the Incarnation of Jesus) is celebrated instead on 25 March, nine months before Christmas Day. (With material from: Wikipedia)