CNN News:公历2020年为闰年 全年共有366天

Which of these historic calendars was created the most recently?
Julian calendar, Byzantine calendar, Hebrew calendar, or Gregorian calendar?
The Gregorian calendar, which is widely used today was proclaimed in 1582.
And it includes a date that only comes along every four years — leap day, February 29th. This year that happens to be this Saturday. February ends on the 28th in non-leap years.
So why do we have the extra day? It's the earth's fault. On the Gregorian calendar at least, it doesn't complete its orbit in exactly a year.
GEOFF CHESTER, U.S. NAVAL OBSERVATORY: It goes around the sun once in 365 and almost a quarter day. Almost but not quite. So, in order to rectify this, we have to periodically add an extra day to the calendar.

 AZUZ: That happens every four years, hence the leap day. And it coincides with presidential election years in the United States.
Besides that though, does it matter that 2020 will have 366 days? Well, those who were born in the leap year on February 29th will actually get to celebrate their birthdays on the 29th instead of on February 28th or March 1st.
And there is some interesting history associated with leap years. According to Irish tradition, years with 366 days were years when women could propose to men when it was the other way around in non leap years. Beyond that though, well, you only get to say happy February 29th every four years, so go crazy with that y'all.