The Day of the Dead celebrations in Mexico developed from ancient traditions among its pre-Columbian cultures. Rituals celebrating the deaths of ancestors were 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. It 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.

By the late 20th century in most regions of Mexico, practices had developed to honor dead children and infants on November 1, and to honor deceased adults on November 2. November 1 is generally referred to as Día de los Inocentes (“Day of the Innocents”). Also as Día de los Angelitos (“Day of the Little Angels”); November 2 is referred to as Día de los Muertos or Día de los Difuntos (“Day of the Dead”).

In the 2015 James Bond film, Spectre, the opening sequence features a Day of the Dead parade in Mexico City. At the time, no such parade took place in Mexico City; one year later, due to the interest in the film and the government desire to promote the pre-Hispanic Mexican culture, the federal and local authorities decided to organize an actual “Día de Muertos” parade through Paseo de la Reforma and Centro Historico on October 29, 2016, which was attended by 250,000 people. Source: Wikipedia.