Copernicus was born on February 19, 1473 and the Reformation of the Calendar was issued on February 24, 1582 by the Pope Gregorius XIII, because the real equinox was occurring on March 11, instead of March 21 according to Nicea’s Council prescriptions of 325 AD on the Easter Computus. The Gregorian Reformation solved the real equinox date problem, known by all scholarly people (e.g. Dante Alighieri Ma prima che gennaio tutto si sverni / per la centesma ch'è là giù negletta Par XXVII 142-143). We can see the effectiveness of the Reformation measuring the ingress of the Sun in Pisces this year 2023 by using the historical meridian lines of St. Peter’s square in Vatican (1586-1817) and of St. Maria degli Angeli (1702). With the latter instrument we made also the angular measure of the meridian arc from Rome to Motta di Livenza, repeating the Eratostenes experiment with the Cassini corrections for the atmospheric refraction, obtaining the Earth’s circumpherence within 1‰, and showing why the giant pinhole meridian lines have been preferred for solar astrometry up to two centuries after the invention of the telescope.