날짜 더하기
function dateAdd($orgDate,$mth){
 $cd = strtotime($orgDate);
 $retDAY = date('Y-m-d', mktime(0,0,0,date('m',$cd),date('d',$cd)+$mth,date('Y',$cd)));
 return $retDAY;
}

날짜 차이 구하기

function dateDiff($date1, $date2){
 $_date1 = explode("-",$date1);
 $_date2 = explode("-",$date2);

 $tm1 = mktime(0,0,0,$_date1[1],$_date1[2],$_date1[0]);
 $tm2 = mktime(0,0,0,$_date2[1],$_date2[2],$_date2[0]);

 return ($tm1 - $tm2) / 86400;
}

날짜에 해당하는 요일구하기

function dateName($date){
 $date_1=substr($date,0,4);
 $date_2=substr($date,5,2);
 $date_3=substr($date,8,2);
 $t_i=mktime(0,0,0,$date_2,$date_3,$date_1);
 $date_show=date('D',$t_i);

 switch($date_show){
  case('Mon'):echo "월";break;
  case('Tue'):echo "화";break;
  case('Wed'):echo "수";break;
  case('Thu'):echo "목";break;
  case('Fri'):echo "금";break;
  case('Sat'):echo "토";break;
  case('Sun'):echo "일";break;
 }
}