Did you know?
Despite progress made in astronomy and mathematics, the Julian calendar, instituted in 46 B.C., was still in use in the sixteenth century. Based on a year lasting 365¼ days, it accumulated a ten-day gain on the mean tropical year of 365.24219 days, thus drifting with respect to the equinoxes, solstices and seasons. After numerous attempts, in 1582 Pope Gregory XIII introduced the necessary reform by following Thursday October 4th by Friday October 15th. He also omitted a leap year every one hundred years, except for century years divisible by 400.