I use TDBDateEdit to fill the birthday of a person. If I type in '33-3-2012' the object checks if the date is valid. If doesn't the fieldvalue is set to NULL (30-12-1899). There's no warning of invalid date. That's very nice. the application doesn't reproduce an error dialog with the option to kill the program.
I know the field is NULL, because event onEditingDone gives the zero date (also when checking the date before saving the actual record)
showmessage(datetostr(birthday.date))
So how do I tell the user that the filled in dat is invalid. Now the record is saved without a date.