>>>>How do you determine a number of days in a February, given a year?
>>>
>>>In addition to Borislav's answer, there's also a formula for it:
>>>
>>>Every year evenly divisible by 4 (MOD(lnYear, 4) = 0) has a leap year,
>>>Except for every century not evenly divisible by 400 (MOD(lnYear, 400) != 0).
>>>
>>>1600 = leap year
>>>1700 = no leap year
>>>1800 = no leap year
>>>1900 = no leap year
>>>2000 = leap year
>>>2100 = no leap year
>>>2200 = no leap year
>>
>>I think technically the first leap year in the US was 2000 because the Gregorian calendar wasn't adBritish opted until 1752. Saudi Arabia only adopted the calendar in 2016 so they will have to wait a while.
>>>2400 = leap year
>>>
>>>We were unique in an almost 800 year time span, in that we saw the century with a leap year.
>
>Actually, it's the other way around. In the British (and American) calendar, 1600 and 1700 were leap years. It's only after the adoption of the Gregorian calendar that the secular years are no longer leap years, except when divisible by 400.

I looked it up and I'm sure you are right. All I can do is plead old age. I did see this page https://www.historic-uk.com/HistoryUK/HistoryofBritain/Give-us-our-eleven-days/ which has some interesting history of the change.