This is not about the horror/zombie movie franchise of cinema. No, Dia de los Muertos is an integration of ancient indigenous Mexican traditions from among its pre-Columbian cultures and the teachings of the Catholic Church in New Spain (Mexico).
Rituals celebrating the deaths of ancestors had been observed by these civilizations perhaps for as long as 2,500–3,000 years. The festival that developed into the modern Day of the Dead fell in the ninth month of the Aztec calendar, about the beginning of August, and was celebrated for an entire month. The festivities were dedicated to the goddess known as the "Lady of the Dead", corresponding to the modern La Calavera Catrina.
The Catholic Traditions of Allhallowtide: All Saints Eve October 31, All Saints Day November 1 and All Souls Day November 2, a "time to remember the dead, including martyrs, saints, and all faithful departed Christians." fit closely with the beliefs of many of the indigenous.
The multi-day holiday involves family and friends gathering to pray for and remember friends and family members who have died, cleaning and repairing the graves and helping support their loved ones spiritual journey. In Mexican culture, death is viewed as a natural part of the human cycle. Mexicans view it not as a day of sadness but as a day of celebration because their loved ones awake and celebrate with them.
The three-day celebration, the Day of the Dead: On October 31, All Hallows Eve, the children make a children's altar to invite the angelitos (spirits of dead children) to come back for a visit. November 1 is All Saints Day, and the adult spirits will come to visit. November 2 is All Souls Day, when families go to the cemetery to decorate the graves and tombs of their relatives. The three-day fiesta is filled with marigolds, the flowers of the dead; muertos (the bread of the dead); sugar skulls; cardboard skeletons; tissue paper decorations; fruit and nuts; incense, and other traditional foods and decorations.