<?php
    $date=array('2009-03','2010-01','2009-02');
    for ($i=0;isset($date[$i]);$i++) {

    $datess=explode('-',$date[$i]);

    $dates[$i]= $datess[0].'-'.$datess[1];
    //unset($datess);
    
}
    print_r($dates);
?>

Array
(
    [0] => 2009-03
    [1] => 2010-01
    [2] => 2009-02
)