All Souls Day (Nov. 2) is a Roman Catholic day of remembrance for friends and loved ones who have passed away. It developed alongside All Saints Day (or the Feast of All Saints), celebrated on Nov. 1st.
The traditions of the Feast of All Souls began independently of the Feast of All Saints. The Feast of All Souls owes its beginning to seventh century monks who decided to offer the mass on the day after Pentecost for their deceased community members. In the late tenth century, the Benedictine monastery in Cluny chose to move their mass for their dead to November 2, the day after the Feast of all Saints. This custom spread and in the thirteenth century, Rome put the feast on the calendar of the entire Church. The date remained November 2 so that all in the Communion of the Saints might be celebrated together.