As a sidenote. The only reason this is an issue is because our ancestors didn't know math. The concept of 'zero' hadn't been invented yet in Europe, when a monk in the 6th century came up with our current numbering of years. This brings about all kinds of mathematical and logical problems; for example counting down from the year 500 to 500BC is 999 years, instead of 1000 like what your calculator tells you or if you would count up from 500 to 1500. Having no 0 means we've mistakenly skipped a year, which would also be a leap year. In astronomy they actually do have a year 0 because of that (1BC, and then -1 is 2BC), starting centuries at the 0s.