The leap year system we follow today is part of the Gregorian calendar, named after Pope Gregory XIII, who introduced it in October 1582. This calendar aimed to correct the discrepancies in the Julian calendar, which underestimated the solar year by about 11 minutes. ...
March. Two other months (Intercalaris PriorandIntercalaris Posterior) were added after November. (Note, this explains why leap years are also known as intercalary years.) The end result was a year that was fifteen months and 445 days long, and was nicknamedAnnus Confusionus, “Year of ...