«LUNARIO NOVO» OF 1582: THE GREGORIAN REFORM OF THE CALENDAR
The Julian calendar, named and established by Julius Caesar in 46 BC, structured the calendar year in 365 days and the added a day every 4 years (leap year), in order to compensate for the lack of balance of almost 6 hours between the calendar year and the solar one; on the basis of that calculation, which seemed to be exact, the vernal equinox was established for the 25th March and the winter solstice for the 25th December. As the centuries went by, a calculation mistake in the Julian calendar was detected, which added a day every 128 years and therefore shifted the equinox and the solstice. Since the Church determined the movable liturgical feasts according to the Easter, which was in its turn linked to the vernal equinox, it was then became urgent to modify this calendar. Among the many reform attempts, we recall the one supported by the Council of Trent, which was the one Gregory XIII worked on.
According to the studies of the Calabrian physician and astrologer, Luigi Lilio, the pope established the new calendar with the aforementioned bull, thus avoiding the inconveniences of the one then in force by abolishing 10 days in the month of October: so with the papal decree, the month of October in 1582 was deprived of the days between the 5th and the 14th inclusive, so after the 4th, it was directly the 15th. …
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