October 5, 1582 never happened: the calendar was worked out by a physician from Cirò
In 1582, in Italy, Spain and Portugal, Thursday October 4 was followed directly by Friday October 15: ten days struck out to bring the spring equinox back to March 21. The reform decreed by Pope Gregory XIII in the bull Inter gravissimas of February 24, 1582 rested on the calculations of Luigi Lilio, a physician, astronomer and mathematician born, by tradition, in 1510 in Cirò, in Calabria at the toe of Italy. Lilio never saw his calendar in use: he died between 1574 and 1576, and it was his brother Antonio who presented the project to the papal commission. A crater on the Moon now bears his name, and since 2012 Calabria has marked March 21 as Calendar Day.
