O.K:
My initial value looks like this:
$field_03=\"7/23/2002\";// and then I have tried
$field_03=eregi_replace(\"/\", \"-\",$field_03);
$field_03=explode(\"-\",$field_03);
$field_03=mktime(0,0,0,$field_03[2],$field_03[0],$field_03[1]);//Here trying to move the year to the begginig of the array but it return -1.
Thanks in advance fr any help.