Thanks for reporting that Joseph.

I had a little difficulty reproducing it. I was only able to
do it if I submitted an invalid date and got an error.

Once I did that the bad date was passed to the calendar popup.

I have changed to code to catch the error and highlight today's date in
the calendar.

I will open a new issue/feature request to enhance the calendar
popup and javascript code to use the current value in the date
field rather than the last submitted value.