>>>
>>>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.

When the change was first introduced in what was then called the Papal countries, in 1582, only 10 days were skipped (and there was also some commotion around it), precisely because by the 18th century an extra non-leap secular year had already been passed.

Another curiosity, if you fancy it: the difference for the adoption of the reform sparked the coincidence of Shakespeare and Cervantes dying on the same day (when, in fact, they died 11 days apart).

Bringing some VFP focus into this: https://github.com/atlopes/calendar

DO LOCFILE("british-calendar.prg")
m.BC = CREATEOBJECT("BritishCalendar")
m.BC.SetDate(m.BC.AdoptionYear, m.BC.AdoptionMonth, m.BC.AdoptionDay)
? m.BC.DTOS()   && displays 17520914
m.BC.DaysAdd(-1)
? m.BC.DTOS()   && displays 17520902
m.GC = CREATEOBJECT("GregorianCalendar")
m.GC.SetDate(m.BC)
? m.GC.DTOS()  && displays 17520913
* meaning that 17520913 in the Gregorian Calendar is 17520902 in the British Calendar