time difference function not working

[dingus]

hey guys i got this function to calculate the difference between a original data and now

 

but for the life of me i cant work out why but it is outputting the wrong difference (out by a few days)

 

anyway here is the function

 

function timeDiff($difference) {

        $periods = array(
        'millennia' => 31556926000,
        'century' => 3155692600,
        'decade' => 315569260,
        'year' => 31556926,
        'month' => 2629743,
        'week' => 604800,
        'day' => 86400,
        'hours' => 3600,
        'minutes' => 60,
        'seconds' => 1
        );

        
        
foreach ($periods as $label => $value) {
      $difference1 = $difference / $value ;
      if($difference1 < 1){
          
      }else{
       $str .= floor($difference1) . $label . " " ;
       $difference = $difference - ($value * floor($difference1));
      }
    }

return $str ;    
    
}

 

any insight will be helpful