Many holidays in Mexico are also celebrated in the United States, such as Christmas, Easter and New Year's Eve. These are the largest holidays and are always celebrated with days off of school and work. However, Mexico also has holidays that we do not celebrate in the United States. One of those holidays is Dia de Muertos, or Day of the Dead.
Dia de Muertos is celebrated every year on November 1st and 2nd, although the decorating usually begins at least a week in advance. The belief is that the souls of all those who have died can come back to earth during that time, with infants and children returning on November 1st and adults returning on November 2nd. During this time, people build ofrendas, or altars, with pictures of their lost loved ones, as well as flowers (especially marigolds), skulls made of sugar, tissue paper art, candles or incense, and anything else that would honor the dead.
This tradition is believed to have started with the Aztecs in southern Mexico, where it was the celebration of the goddess of the afterlife, Mictecacihuatl. It was not originally celebrated in northern Mexico, where the Aztecs had less influence.