WCMO are the nongs who developed MS Excel. It doesn't recognise dates prior to 1900 as it stores a date as the number of days that have elapsed since January 1, 1900 . However, it does recognise dates forward to 9999. I mean, really?
So dates in the nineteenth century & before can't be formatted as a 'date'. It remains as text, so, for instance, sorting a column of mixed dates will not work.
Appreciate
@exceladdict pointing towards a work-around. You add 1,000 years to each date. As the way dates are 'calculated' by Excel is not straightforward, neither is the adding of 1,000 years, but when you get there, it works.