October 30 and/or 31 is El Dia de los Angelitos, which set for remembrance of deceased infants and children, often referred to as angelitos (little angels). In Mexican Catholic thought, these young souls are sent straight to heaven. Offerings on altars include toys, sweets, a cup of milk, and other treats.
November 1 is offically set aside to venerate the Saints of the Catholic Church. However ofrendas are apparently set up to folks throughout these days. Some sources stated that the altars for the angelitos are set up on November 1.
November 2 is All Souls' Day, which is the Day of the Dead (El Dia de los Muertos) proper. Those who have died as adults are honored on November 2 (All Souls' Day). Private altars are set up in homes. Public altars to heros, celebrities, and other popular individuals who have passed away have offerings of traditional food and drink as well as items associated with them. These public ofrendas are often brightly decorated along with memorial and adorned with festive skulls, skeletons, and bright marigolds. The skeletons are shown playing music, dancing, eating, and drinking.
In the eighth century, the Catholic Church decreed November 1 as All Saints' Day. Setting aside the day to honor the martyrs and saints was an attempt to replace a Celtic tradition which honored their ancestors during the celebration of the new year at the harverst festival, Samhain.
When the conquistadores came over to Mexico, the Catholic observation of All Saints' Day and All Souls' Day got intermixed with with Meso-Americam beliefs and customs about death. Hence these days of the Dead, celebrated throughout Mexico, coincide with the Christian All Souls' and All Saints' days, November 1 and 2. The Church attempted to institute an observance with a suitably serious day of prayer and focusing attention and admiration on the saints and martyrs, and a somber reflection on human mortality and death. However, the people of Mexico did not fully adopt the early priests' ideas.
A pre-Hispanic survival seems to be the predominance of yellow marigolds, as yellow was the Aztec color of the dead. Likewise, in the pre-Hispanic era, apparently the Aztec calendar called for festivities in remembrance of deceased children, called Miccailhuitontli (Little Feast for the Dead), which was around the time of the harvest.
The Days of the Dead are celebrated not only thoughout the USA southwest and California by Mexican-Americans and other Hispanics, but in any place that Hispanic communities have sprung up. Thus, the custom of setting up public and private ofrendas has spread throughout the USA. In the way that cultures swap customs, some Mexican-American communities are now adopting the American custom of children trick-or-treating on October 31.
The celebration of El Dia de los Muertos has also influenced Neo-Pagan/Wiccan practices of honoring their beloved dead.
Observing elaborate Hispanic ofrendas, or altars to the dead, Neo-Pagans/Wiccans got the idea of making more elaborate altars with more items. Due to Gerald Gardner's comments about the "Mighty Dead" many Wiccans were already honoring their own deceased loved ones by putting their photos upon their Samhain altars. Starhawk has mentioned the practice of setting up altars, similar to ofrendas specifically honoring one's own deceased loved ones in several of her books. This practice seems to have been absorbed into the Wiccan/Pagan community in the mid 1980's. This process was termed by Robert Cantwell as "ethnomimesis," the unconscious mimicry by which people adopt customs, traditions, or other aspects of culture. Another example of "ethnomimesis" is Mexican-American/Latino communities adopting the American custom of trick-or-treating.
Skulls and skeletons have been part of American Halloween decoration and symbology for many years.1 Hence, Day of the Dead skull decorations have also found their way onto Neo-Pagan altars during Samhain. These skulls are decorated with festive designs and bright colors of red, green, white, and black. At least one source alleged that the different colors on the skulls had different "magical" meanings. Green is for financial success; red is for love; white is for luck or blessings; black is for protection. It's an intersting thought but I'm not certain many Catholic Mexicans actually hold any belief in this idea of magical color association involving the colors decorating a calavera de azucar. In fact, I understand that it is common to decorate a sugar skull and write on it the name of someone who has died in icing.
1 Early American cartoons and movies, for example, show cavorting skeletons without any direct borrowing from Hispanic culture. The image most probably relates back to very early British images of the Grim Reaper. One could even attempt to draw a link between the ancient Celtic veneration of skulls and modern skull images on Wiccan altars, but that is not in the scope of this brief article.
2007, Myth Woodling
I originally created the above article as a handout for a CPC Samhain event in November.
Update 2013: As indicated by an article in Tu Revista Latina Magazine, Me da mi calaverita?: el Halloween y el Día de Muertos , 2012, the American custom of trick-or-treating has definitely become practiced in parts of northwestern and central Mexico. In different regions, the "Dulce o truco!" (an adaptation of the English "Trick or treat!") or Trikotrit! has been replaced with "Queremos Halloween!" or "Calaverita?" or "Me da mi calaverita?" ("Will you give me my little skull?"). Calaverita (little skull) was a request for the traditional treat calavera de azucar ("sugar skulls") or other sweets.
Update 2016: Glancing at this article around the Day of the Dead in November, I noticed and corrected several spelling errors.