Of all ancient Pagan holiday now celebrated in modern times, Samhain seems to have been most modified and the most diversely observed. Celebrated on October 31st, many start rituals and feasts late in the evenings near midnight, carrying them into the next day November 1st. From what I have found in my research is that Samhain originated as a High Day in the Celtic culture. From the Christianization of the high day to the modern re-creation by Neo-Pagan groups to make it their special day, to reconstruction groups that dig through historical records seeking a more tradition version, there are basic ties that bind all the different views; those of honoring the dead and the end of the harvesting season.
The Christianization of the Celtic High Day happened sometime in the mid 730’s C.E. by Pope Gregory III with the moving of the Catholic holiday ‘All Saints Day’ from May 13th, which was created by Pope Boniface IV around 600 C.E.. The origin of All Saints Day is based on the consecration of the Pantheon in
Rome to the Virgin Mary, the date was chosen because
it was the date of the Roman pagan holiday of Feast of Lemures. Feast of
Lemures was a celebration in which the Romans expelled the malevolent fearful
spirits and ghosts of the dead from their homes. This was done by chanting
incantations while tossing black beans over the shoulder and clanging bronze
pots at midnight. Once the date was changed to November 1st by
Gregory III the Church tried to disassociate their faith from any pagan
connection by making the holiday so that it had a focus on saints as well as
martyrs, which in the end were still usually long dead individuals said to
visit the living to help inspire and guide the faithful. In modern times
Christians, other than Catholics, celebrate the holiday as Halloween. It is
celebrated as a time for children to dress in customs for witches, ghosts,
demons, and the dead to venture out into the night chanting the childhood
phase, ‘Trick or Treats’.
For Neo-Pagans, Samhain is one of four cross quarter or fire festivals. It is seen as both the ending and the beginning of the year. The majority of celebrations start their rituals late in the evenings sometimes around 11 to midnight which will allow them to carry into the New Year. This time is seen as being one of two times during the year that the walls between the worlds thin or completely dissolve allowing the mortal world to commune with the spirit world and that of the dead as well. It is a festival of dark and death that it is perfectly balanced with its cross quarter festival Beltane, the second time of year when the walls of all worlds thins. Many also see this as a time to have deeper connections with their deities seeking guidance through divination and trance work.
From what historians have been able to learn, we believe that the Celts saw the world as being divided into times, a time of darkness and a time of light. Samhain was seen as the beginning of the dark time of the year. For Celtic Reconstructionists Samhain is not celebrated about a specific date as it is with modern times but around the first frost of the year, with the Celts being an agrarian society this would fit. With this being the end of the harvesting season it was a time to take stock of all the food stores and to decide what live stock would need to be taken as food for the coming winter. Traditionally at ritual time all fires were put out through the town or village. There would be two large bonfires built near each other that celebrants and live stock would press between for blessing and purification. Offerings where given to the gods as well as those who had passed beyond and all the ancestors. The belief that the walls between the different worlds become thin if not totally lifted during this time of year so the spirit worlds could come through into the mortal realm seems to have its start here in the Celtic culture and their rituals seem to reflect this. As people left to return home to their feasts, they would light torches from the bonfires with which they would then light their hearth-fires. This helped create the connection with the past as well as with the rest of the community, from there the rest of the fires in the home where lit. During the feasting a place was set for the ancestors and newly departed. In modern times some Reconstructionists will open a door or window, if possible facing the west, to welcome in the ancestors with a candle placed in front to guide them homeward.
Within the Hellenic world honoring the dead was a very important part of the culture. From my studies so far, granted they have been limited, there was no actual official festival for the dead. In many cases this was left up to the individual cities and those who governed them. The dead were offered many of the same gifts as the gods were offered. From some of the things I have read it seems in some cases they even feared the dead so these offerings where given to help keep them complacent. For the modern day usages Samhain could very easily be used in a Greek format to honor the dead in the same way it is used by most pagans. As for honoring Greek deities, this would be a great time to honor the Lord and Queen of the dead, Hades and Persephone. As Persephone took Her seat at the side of Her husband Hades, She becomes the Queen of the Dead. Together They watch over those who have passed into the underworld. Samhain gives people the chance to honor the two deities that one day they will stand before after this life.
Even though Samhain may have originated with the Celts, like many other valuable cultural, intellectual, and technology gifts left to us by them, it has far wider influences throughout the modern world just as they did in the ancient world.