$date = DateTime::createFromFormat('Y-m-d H:i:s',$row['date'],new DateTimeZone('UTC'));
$now = new DateTime(NULL,new DateTimeZone('UTC'));
$int = $date->diff($now);
$days = $int->format('%d');
if( $days >= 14 && $days < 21 ) {
// 2 weeks
} elseif( $days >= 21 ) {
// 3 weeks+
}
Of course if you aren't actually using the date from the DB with anything else all this can be done in the select query.