If your date is stored in that state...meaning your field actually says "1980-01-01"...
You could do an explode..
$dbDate = extracted date from db;
$oldDate - explode('-', $dbDate);
Which will give you an array of the 3 values of year, month an date.
Then, do a list...
list($year, $month, $day) = $oldDate;
Then set $year...
$year = date("Y");
$newDate = $year."-".$month."-".$day;
Insert $newDate back into the db. Done.
Oh, just realized you DON'T want to update the table value. Hmmm, yeah, the above won't help then. Sorry! I'll leave my post just in case it helps at all.