Giselbert van de Bidgouw - Birth

Excellent Point :-) Taking a look... or have you figured out where the error is already?

https://nl.wikipedia.org/wiki/Giselbert_I - birthdate c 825

Still not right his son was born c 790 and Wikipedia doesn't give a date but I think this far back its just guess work as no records were kept as only priests etc could read or write.

I'm obviously not seeing what you're seeing. Am I just being stupid?
I have the father born c 800 and the son c 825 - While the dates are obviously just estimated - that wikipedia link does give them.