On September 27th, 2021, Mexico celebrated the bicentennial of Mexican independence.  There was a big celebration in Mexico City's Zocalo plaza. President Biden sent greetings. A pair of Russian cosmonauts sent congratulations from space. Other nations sent congratulations as well.

Wait, didn't Mexico already have its bicentennial?

Well, yes, eleven years ago, in 2010, as I reported in my VDARE.COM article entitled VDARE.Com Wishes Mexicans A Happy Bicentennial/Centennial—In Mexico.

In 2010, Mexicans celebrated two anniversaries: 1) The bicentennial of the 1810 movement which developed into an independence movement and, 2) the Mexican Revolution, which began in 1910.

Mexican Independence Day, on September 15/16, celebrates the beginning of the Hidalgo uprising. That was in 1810, when Catholic priest Miguel Hidalgo gathered a crowd and rang a bell in front of a church in the town of Dolores, calling for the multitude to rise up against the government of the Spanish viceroy.

Hidalgo wasn't actually calling for independence from Spain, which was then occupied by Napoleon's Army. But after Hidalgo's execution in 1811, the movement continued and eventually developed into an independence movement.

Mexican independence was actually achieved in 1821, when royalist general Agustin de Iturbide made a deal with insurgent leader Vicente Guerrero, and the two leaders formed the Army of the Three Guarantees—religion, independence and unity.

On September 27th, 1821, the Army of the Three Guarantees marched into Mexico City and took control.

The next day, September 28th, 2021, the Mexican Declaration of Independence was drafted and signed. Its official name in Spanish was the Acta de Independencia del Imperio Mexicano. Unlike the U.S. Declaration of Independence, the Mexican Declaration of Independence was drafted upon achieving independence.

The last Spanish Viceroy, who signed off on Mexican independence, was Juan O'Donojú, a Spaniard of Irish descent (O'Donojú is the Hispanicized form of O'Donoghue).

Back in Spain, the Spanish government refused to recognize Mexican independence until 1836. Mexico was the first former colony it recognized.

To summarize, September 16th celebrates the start of the public uprising in 1810, while September 27th celebrates when independence was actually achieved in 1821.  

Both September 16th and September 27th have been celebrated in the past in Mexico, but nowadays it's the 16th that is celebrated.  But this year is the bicentennial of the September 27th date, so it's being celebrated as a bicentennial.