Custom WP_Query to get posts from a specific date range from a range of years.

date-range-query.php

<?php 
$dates = ['relation'=>'OR'];
$x = 1;
while( $x <= 5 ) : 

	$currentDate = new DateTime();
	$previous_date = $currentDate->sub( new DateInterval( "P{$x}Y" ) );
	$previous_year = $previous_date->format('Y');
	
	$currentDate = new DateTime();
	$previous_days = $currentDate->sub( new DateInterval('P15D') );
	$previous_day  = $previous_days->format('m-d');
	
	$currentDate = new DateTime();
	$future_days   = $currentDate->add( new DateInterval('P15D') );	
	$future_day    = $future_days->format('m-d');
	
	$dates[] = [
		'after'  => $previous_year . '-' . $previous_day,
		'before' => $previous_year . '-' . $future_day,
		'inclusive' => true,
	];

  $x++;
endwhile;

$args = [
	'date_query' => $dates
];

$r = new WP_Query($args);

/*
[request] => SELECT SQL_CALC_FOUND_ROWS DISTINCT wp_posts.ID FROM wp_posts  WHERE 1=1  AND ( 
  ( wp_posts.post_date >= '2019-08-25 00:00:00' AND wp_posts.post_date <= '2019-09-24 23:59:59' ) 
  OR 
  ( wp_posts.post_date >= '2018-08-25 00:00:00' AND wp_posts.post_date <= '2018-09-24 23:59:59' ) 
  OR 
  ( wp_posts.post_date >= '2017-08-25 00:00:00' AND wp_posts.post_date <= '2017-09-24 23:59:59' ) 
  OR 
  ( wp_posts.post_date >= '2016-08-25 00:00:00' AND wp_posts.post_date <= '2016-09-24 23:59:59' ) 
  OR 
  ( wp_posts.post_date >= '2015-08-25 00:00:00' AND wp_posts.post_date <= '2015-09-24 23:59:59' )
) AND wp_posts.post_type = 'post' AND (wp_posts.post_status = 'publish' OR wp_posts.post_status = 'private')  ORDER BY wp_posts.post_date DESC LIMIT 0, 12
*/