>No, it's simply limited to 1753 and later because that's when the English-speaking countries standardized on the Gregorian calendar.

Thanks Tamar, Bob Velke has already pointed me in this direction.

But, how about Eastern European countries, which adopted (a slightly different) Gregorian calendar in 1924, does GOMONTH() know it?

After some reading on what pope Gregory did in 1582 to fix what emperor Julius Caesar did in (what we now call) 46 BC to fix the roman calendar, I come to agree with Bob that “The whole idea of a reliable (FP/VFP - my note) Julian or Gregorian date back that far (1753 – my note) is just laughable anyway.”

I'd say that the current behavior of GOMONTH() in regard to the year of 1753 is not warranted, and not documented (does this qualify it as a bug?), and that it should behave like all other date math calculations in FP/VFP – i.e. happily go back to 1 Mar 0000.