Hi Courtney
The "dates" in the keyword table are actually stored in the table as the text equivalent, in iso format. (yyyy-mm-dd, which is SQL Server's native format, more or less). When you enter a date using the little date-picker, the date you select is presumably converted to that format, and then saved. It's probably that conversion that doesn't cope with 1800-y dates.
There is a bit of a work-around, I think, by changing the keyword definition,which would only work if you only need to enter a limited set of dates. That is, you wouldn't want to leave this setup in place - just switch it on, enter your early dates, then switch it off again. By the sound of it, that might be ok for what you need to do.
If you
That date will display correctly, although you won't be able to edit it without doing the switch again, of course. And it may not report correctly, although it probably will. It certainly works fine in List Manager.
HTH
Ken