<?php 

$current_year = date('Y', current_time('timestamp'));

if(!$_GET['month']){
	$current_month = date('m', current_time('timestamp'));
	$display_month = date('F',current_time('timestamp'));
}else{
	$current_month = $_GET['month'];	
	$thedate=strtotime($current_year.'-'.$current_month);
	$display_month = date('F',$thedate);
	$display_year = date('Y', $thedate);
}

$cat_id=4;

$args = array( 
	'orderby' => 'date',
	'post_type' => 'post',
	'cat' => $cat_id,
	'posts_per_page'	=> 1,
	'date_query' => array(
        array(
            'year'  => $current_year,
			'month' => $current_month,
        ),
    )
	
);

?>