I'm stumped.
Me too
We do not use 1/1/1900 as a default anywhere. But I believe, so don't be discouraged
.... however :errm: I cannot reproduce your behavior. I just followed your steps from above and when I create a new row, it appears as 1/1/1800.

I think that is the first mystery that we need to resolve. I think that if we clear that up then the rest is downhill. 