Week and day

Is’it possible to configure working week of 5 days and working day of 8 hours in the summary of time of actions? Thanks
I have modified date.lib.php

ConvertSecondToTime($iSecond,$format=‘all’,$lengthOfDay=28800) //28800->5 days


if ($format == ‘all’)
{
if ($iSecond === 0) return ‘0’; // This is to avoid having 0 return a 12:00 AM for en_US

	$sDay=0;
	if ($iSecond \>= $lengthOfDay)
	{   
		for($i = $iSecond; $i \>= $lengthOfDay; $i -= $lengthOfDay )
		{
			$sDay++;
			$iSecond-=$lengthOfDay;
		}
	}
            
	$sTime='';
	/**********MODIFIED***********/
	if ($sDay)
	{	
		if ($sDay \> 4)
		{
			$sWeek = (int) ( ( $sDay \- $sDay % 5 ) / 5 );
			$sDay = $sDay % 5;
                            $weekTranslate = $langs-\>trans("DurationWeek");
                            if ($sWeek \>= 2) $weekTranslate = $langs-\>trans("DurationWeeks");
			$sTime.=$sWeek.' '.$weekTranslate.' ';
		}
                    if ($sDay\>0)
                    {
                        $dayTranslate = $langs-\>trans("Day");
                        if ($sDay \> 1) $dayTranslate = $langs-\>trans("Days");
                        $sTime.=$sDay.' '.$dayTranslate.' ';
                    }
	}.....

Thanks. I will add option into CVS (firstly as a hidden option)

I downloaded new Beta and pre-release versions but I don’t found this option: could you tell me where is?
Thanks