All Souls/All the Faithful Departed
O God, the Maker and Redeemer of all believers: Grant to the faithful departed the unsearchable benefits of the passion of your Son; that on the day of his appearing they may be manifested as your children; through Jesus Christ our Lord, who lives and reigns with you and the Holy Spirit, one God, now and for ever. Amen.
Here is a brief explanation of how All Hallow’s Eve, All Saints’ Day, and All the Faithful Departed are related from An Episcopal Dictionary of the Church/Glossary, see https://www.episcopalchurch.org/glossary/
All Hallows’ Eve
The evening of Oct. 31, which precedes the church's celebration of All Saints' Day on Nov. 1. The BOS provides a form for a service on All Hallows' Eve. This service begins with the Prayer for Light, and it includes two or more readings from scripture. The options for the readings include the Witch of Endor (1 Sm 28:3-25), the Vision of Eliphaz the Temanite (Jb 4:12-21), the Valley of Dry Bones (Ez37;1-14), and the War in Heaven (Rv 12:[1-6]7-12). The readings are followed by a psalm, canticle, or hymn, and a prayer. The BOS notes that “suitable festivities and entertainments” may precede or follow the service, and there may be a visit to a cemetery or burial place. The popular name for this festival is Halloween. It was the eve of Samhain, a pagan Celtic celebration of the beginning of winter and the first day of the new year. This time of the ingathering of the harvest and the approach of winter apparently provided a reminder of human mortality. It was a time when the souls of the dead were said to return to their homes. Bonfires were set on hilltops to frighten away evil spirits. Samhain was a popular festival at the time when the British Isles were converted to Christianity. The church “adopted” this time of celebration for Christian use by observing All Saints' Day on Nov. 1, and All Hallows' Eve on the evening of Oct. 31.
All Saints’ Day
Commemorates all saints, known and unknown, on Nov. 1. All Saints' Day is one of the seven principal feasts of the church year, and one of the four days recommended for the administration of baptism. All Saints' Day may also be celebrated on the Sunday following Nov. 1.
All Faithful Departed
This optional observance is an extension of All Saints' Day. While All Saints' is to remember all the saints, popular piety felt the need to distinguish between outstanding saints and those who are unknown in the wider fellowship of the church, especially family members and friends. Commemoration of All Faithful Departed did not appear in an American Prayer Book until 1979, and it is celebrated on Nov. 2. It is also known as All Souls' Day. Many churches now commemorate all the faithful departed in the context of the All Saints' Day celebration.