The residents of Mexico City celebrate several festivals & events throughout the year.
Dia de los Reyes Magos (Epiphany) ( Wikipedia )January 6th, every year
Dia de los Reyes Magos or Three Kings Day is the day when gifts are exchanged in a traditional manner. In the distant past, January 6th was the day when the Three Kings arrived at the Nativity to give their gifts to baby Jesus. On this day, the Rosca de los Reyes (King's Loaf) is served, a round doughnut-like cake, which contains a little plastic doll somewhere inside. By tradition, if you are served the slice that contains the doll, you must host a party on Dia de la Candelaria in February.
Dia de la Candelaria (Candle Mass Day)February 2nd, all over Mexico
Those who were served the plastic doll in their Three Kings Loaf (see January events, above) host a party on this day. It is a religious holiday, celebrated with dancing, music, processions, bullfights and the blessing of the seeds and candles.
Dia de la Independencia (Independence Day)September 16th
September 16th is Mexico's most important and revered National Holiday. It is an official holiday that commemorates Mexico's Constitution. From the evening of September 15th, festivities begin in the city. At 11pm, the president of the Republic shouts the Cry (El Grito) of "Viva Mexico" from the balcony of the National Palace - an event televised and broadcast on radio to every nook and cranny of the nation, as Mexicans cry back with "Viva!" in a deeply traditional annual ritual. The Zocalo in Mexico City brims and buzzes with unabated excitement. Celebrations are particularly lively at the revolutionary Colonial centres, especially Queretaro and San Miguel de Allende - important and significant places before, during and after the war of Independence from Spain.
Carnaval ( Visit Site )Late Feb/Early March
This festival takes place 46 days before the Easter Sunday (3rd day preceding Ash Wednesday). The carnival kicks off a five-day celebration of the libido before the Catholic lent. Beginning the weekend before Lent, the carnival is celebrated with full enthusiasm accompanied with parades, floats and dancing in the streets.
Di de Nuestra Senora de Guadalupe ( Wikipedia )December 12th
Not a public holiday, but it is probably Mexico's biggest religious festivals of the year. The people of Mexico celebrate the Nuestra Senora de Guadalupe (Our Lady of Guadalupe) with a mass ceremony and a traditional fair in honour of Lady Guadalupe. The day is packed with free concerts on the Basilica de Guadalupe's plaza.
Dia de los Muertos ( Wikipedia )November 1st and 2nd
This event encompasses 2 days: All Saints’ Day, and All Souls’ Day. The first event honours all saints and people who died as children and the event later commemorates the souls of those who died in adulthood. During this time, one can watch sugar-candy skulls, skeletons and Pan de Muerto (Bread of the Dead) advertised in shops and supermarkets as they are a traditional sight in Mexico at this time of year.
July, every year
It is celebrated in the honour of Virgen del Carmen, by offering flowers. Traditional dances and the musical groups known as conjuntos perform on this day at the San Angel district of Mexico City.
Benito Juarez' Birthday ( Wikipedia )March 21st