Ошибка Maximum execution time of 30 seconds

if ($type == 'date') {
    $rectype = 'date';
    $utcDays = floor($numValue - ($this->nineteenFour ? SPREADSHEET_EXCEL_READER_UTCOFFSETDAYS1904 : SPREADSHEET_EXCEL_READER_UTCOFFSETDAYS));
    $utcValue = ($utcDays) * SPREADSHEET_EXCEL_READER_MSINADAY;
    $dateinfo = gmgetdate($utcValue);
 
    $raw = $numValue;
    $fractionalDay = $numValue - floor($numValue) + .0000001; // The .0000001 is to fix for php/excel fractional diffs
 
    $totalseconds = floor(SPREADSHEET_EXCEL_READER_MSINADAY * $fractionalDay);
    $secs = $totalseconds % 60;
    $totalseconds -= $secs;
    $hours = floor($totalseconds / (60 * 60));
    $mins = floor($totalseconds / 60) % 60;
    $string = date ($format, mktime($hours, $mins, $secs, $dateinfo["mon"], $dateinfo["mday"], $dateinfo["year"]));
}

ini_set('max_execution_time','600');

set_time_limit(0);