How to assign the custom field format as date

Hi, Sir/Miss

in a table, I have a field named CRD, and I want to have another custom field CRDP2 with CRD value +9,
it is successful to input “CRD-9” on the table expression , but It show the date with number.

I want to use the event code in the table, but I did not know how to assign the CRDP2 as date format.

who have the good idea? the following event only assign it with fixed value “some text”

// Row Rendered event
function Row_Rendered() {
// To view properties of field class, use:
//var_dump($this->);
// Row Inserted event
$this->_CRDP2->ViewValue =“Some text”;

}

I found a simple method

date(CRD-9) as custom field, it can work well.