Hi everyone, i have dates defined in a dataobject like so

private static $db = array(
'DateStart'=>'Date',
'DateEnd'=>'Date',
);

when i try to get the Year by
$DateStart->Year() or $DateStart->Format('YYYY') or any kind of function, it's always either blank or i get an error.
I tried everything i could since hours, i still get no results.

So, what is the function i'm meant to use to get the Year, month and day of "Date" Object in the php file ?

Any help is welcome, thanks