El calendario gregoriano es un calendario originario de Europa, actualmente utilizado de manera oficial en casi todo el mundo, denominado así por ser su promotor el papa Gregorio XIII, quien promulgó su uso por medio de la bula Inter Gravissimas.
The Europeans brought with them diseases such as measles and smallpox against which the American tribes had no natural immunity. They spread like wildfire, killing rulers of both the Aztecs and Incas, along with millions of other people.
