Solar Empire--Heavens Above

　　Through the Ancient Greeks and later the Romans, mo dern Western Culture has inherited the Egyptian and Mes opotamian calendar and astronomy. But, even their three hundred and sixty-five day year is not perfect. The yea r, in fact, is three hundred and sixty-five and one-qua rter days long. A difference that may not seem like ver y much, but over a period of centuries, it adds up. Eac h year, a quarter of a day was being lost. So when the Romans inherited the calendar, in one bold stroke, Juli us Caesar declared that every four years an extra day w ould be added to the year, a leap year, thus replacing the four quarter days that had been lost. The Julian ca lendar, as it was known, worked well until the 16th cen tury, when the seasons were noticeably out of alignment again. So, in 1582, a commission under the Pope looked at this misalignment, and like Caesar before hand, sett led the problem by declaration. He removed ten days fro m that year. The problem was that the true year, the ti me it takes for the Earth to orbit once around the sun, is actually slightly less than three hundred and sixty- five and a quarter days.

　　"The Pope created a formula to keep these dates in step. From then, every centennial year would have to be divisible by four hundred to become a leap year. So, th e centennial years of 1700, 1800, and 1900 had no leap years. The first centennial year to have a February 29t h, will be the year 2000. The formula is accurate to wi thin twenty-six seconds a year. So, it will be about th ree thousand, three hundred and twenty years before we need to make another adjustment."