Post #4142979

um actually, leap years are not on every year that's a multiple of 4. modern leap years only land on every multiple of 4 if that multiple of 4 is either a multiple of 400, or not a multiple of 100. this means that most multiples of 4 - like 2024 and 1988 - are leap years, years like 1600 and 2000 are leap years, but years like 1700 and 2100 are not leap years. of course, this is not even to mention history. leap years were introduced by ceasar in the year 45 BC, but people kept adding them every 3 years instead of every 4 years by accident, so as a reaction to that, between 9 BC and 8 AD there were no leap years - the two i just mentioned were leap years and between them were only normal ones. and in 1582, there was a switch over to the gregorian calendar, which included multiple reforms, one of which was the rework of leap years, in which the conditional exclusion of century years was introduced, as it had not previously existed and was causing slight drift - the drift was mitigated by skipping 10 days. and this assumes talking about countries which had switched to the gregorian calendar immediately, which for many places was not the case - but that's beyond the scope of this mess of paragraphs. so, leap years were historically on multiples of three between 45 BC and 9 BC including both, then on every multiple of 4 from 8 AD to 1580 including both; and since 1582 and up until the present and foreseeable future, leap years have been and will be on every multiple of 4 which is not also a century year that's indivisible by 400.