I believe this only happens in Chrome. It requires value assignment to be in "yyyy-MM-dd" format. Try in your C#
txtBirthdate.Text = usr.BirthDate.ToString("yyyy-MM-dd");
This should display the correct value (and it doesn't affect the format of the display).
If will display in this format in other browsers tho. You may want to do some browser detection, e.g.
if (Request.Browser.Browser == "Chrome")
{
txtBirthdate.Text = usr.BirthDate.ToString("yyyy-MM-dd");
} else {
txtBirthdate.Text = usr.BirthDate.ToString("MM/dd/yyyy");
}
but perhaps something more sophisticated