you have used mktime incorrectly
so your timestamp is wrong
so when you convert back your formated date is wrong
use the mktime correctly and things should be fine
example.
$dates=array('29/07/04','30/07/04');
foreach($dates as $date)
{
list($day,$month,$year)=explode("/",$date);
$dday = $day;
$dmonth = $month;
$dyear = $year;
$date1 = mktime(0,0,0,$dmonth,$dday,$dyear);
$date2 = mktime(0,0,0,$dday,$dmonth,$dyear);
echo $date." date1 = ".date('d/m/Y',$date1)." date2 = ".date('d/m/Y',$date2).'<br>';
}
output
29/07/04 date1 = 29/07/2004 date2 = 07/05/2006
30/07/04 date1 = 30/07/2004 date2 = 07/06/2006