I also tried formating it like this:
$archivedate = 'July-2006';
$firstday = date("m-1-y 00:00:00",strtotime($archivedate));
$lastday = date("m-t-y 23:59:59",strtotime($archivedate));
and then i do a mysql select like this:
"SELECT * FROM cmsblogposts where postdatetime between '$firstday' and '$lastday'"
and still no luck.