if I was going to put a date field in a text box, I would probably use a formula to display it. Something like totext({table.field}, "MM/dd/yyyy hh:mm:ss"). You might try added a CRLF into the formatting field to force it 2 lines or 2 formulas 1 like: totext({table.field}, "MM/dd/yyyy") and the other like totext({table.field}, "hh:mm:ss") thereby creating your own display
OR forget the formula, just display the same field 2 times, once formatted to display the date, and the other to display the time.
HTH