Why are leap year?

They were instituted because each year is not 365 days accurate. Indeed, the period in which the earth completes one lap around the sun is 365.2422 days. The leap years has been the way that astronomers found to offset this gap: every four years, adds up one day, the Feb. 29, to our timetable. To learn whether a leap year is, simply apply two rules. First, the year has to be a number divisible by four - 2004, for example, fits that rule.

Second, do not years divisible by 100, except those that are divisible by 400 - is the case of 2000. In practice, almost every year divisible by four are leap. The latest exceptions were the years of 1800 and 1900, and the next will be 2100 and 2200. "These standards were established at the end of the century 16 by Pope Gregory XIII. In his tribute, call our current Gregorian calendar, "says astronomer Amâncio Friaça, USP.

Meanwhile, the first to reform the counting of time was the Roman emperor Julius Caesar, in 46 BC still From this season are some explanations for the curious habit of introducing a day more in a few years. As called Julian calendar, the last month of the year was February. Thus, the "bonus" fell exactly in that period, as happens today. "The difference is that extra day was not the last of the month, but the sixth day before the month of March, which was counted twice. Hence comes the name leap, "says Amâncio. To close, let's solve a mystery: you know what happens to people born on February 29th? In registry the rule is register who came to the world on 29 that same date. Theoretically, the newborn only going to blow the sail every four years. In practice, the "leap" celebrate the date one day before.