为什么会有四年一次的闰日?

摘要

＜正＞At some point in elementary school,your science teacher probably explained to you that there are 365 days in a year because that’s how long it takes for Earth to complete one full rotation around the sun.What they might not have specified,however,is that it’s not exactly 365days—it’s actually closer to 365.2421 days.