Frogprince, I'm unsure as to a connection between Fundamentalists and making date/time calculations.

As far as I have understood it, the term points more to a strict literal bible believing type although the term also seems to me to be rather curiously entangled with (far?) right wing American politics...

The reason why I'm questioning here is that my guess would be that Fundamentalists would be very much in line with (I'd imagine) the vast majority of Christians on this. As such I would expect the usage of verses such as Mark 13:32 ("No one knows about that day or hour, not even the angels in heaven, nor the Son, but only the Father".) to argue that the bible is clear in that this sort of calculation is impossible.

Maybe Campings followers are something else? (I don't know - I'm asking),