The Day of the Dead is a Mexican holiday that has spread in popularity into parts of the United States and across Latin America.
It is celebrated from October 31 through November 2, to coincide with both the American tradition and the Catholic holy days.
All Saints' Say occurs on the same day as the Mexican "Dide los Innocentes" a day dedicated to deceased children.
Across much of Europe, the day is commemorated with offerings of flowers left on the graves of the dead.
Other countries have different rules according to their national bishop's conferences.
The bishops of each conference have the authority to amend the rules surrounding the obligation of the day.
All Souls' Day in on November 2, and it is NOT a Holy Day of Obligation.
Following the establishment of the Frankish Empire, and following the reign of Charlemagne, the holy day, which was already celebrated on November 1, became a holy day of obligation by decree of Pope Gregory IV and Louis the Pious, who was king over a portion of Charlemagne's former empire.
Following the Protestant Reformation, many Protestants retained the holy day, although they dismissed the need to pray for the dead.
Instead, the day has been used to commemorate those who have recently died, usually in the past year, and to remember the examples of those who lived holy lives.
The Catholic practice however, celebrates all those who have entered heaven, including saints who are recognized by the Church and those who are not. In the United States, the day before is Halloween and is usually celebrated by dressing in costumes with themes of death commonly associated.
The choice of the day may have been intended to co-opt the pagan holiday "Feast of the Lamures," a day which pagans used to placate the restless spirits of the dead.