>>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 adopted 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.