>Hardly a bug. Dates following the Gregorian Calendar did not exist before 1752, so what's it supposed to do, guess? :)

Fred,

I don't know if you saw my response to this, but GOMONTH() may be relying on Zoeller's (or Zeller's) Congruence for its calculations. Since this would rely on the adoption of the Gregorian Calendar (I believe), it would explain this behavior. Apparently, it uses 1752 because that's when it was adopted here and in Great Britain. Originally it was introduced in 1582.