Filter Posts and Media Files by a Custom Date Range in Admin Area with no plugins

class mishaDateRange{

	function __construct(){
	
		// if you do not want to remove default "by month filter", remove/comment this line
		add_filter( 'months_dropdown_results', '__return_empty_array' );
		
		// include CSS/JS, in our case jQuery UI datepicker
		add_action( 'admin_enqueue_scripts', array( $this, 'jqueryui' ) );
		
		// HTML of the filter
		add_action( 'restrict_manage_posts', array( $this, 'form' ) );
		
		// the function that filters posts
		add_action( 'pre_get_posts', array( $this, 'filterquery' ) );
		
	}

	/*
	 * Add jQuery UI CSS and the datepicker script
	 * Everything else should be already included in /wp-admin/ like jquery, jquery-ui-core etc
	 * If you use WooCommerce, you can skip this function completely
	 */
	function jqueryui(){
		wp_enqueue_style( 'jquery-ui', '//code.jquery.com/ui/1.11.4/themes/smoothness/jquery-ui.min.css' );
		wp_enqueue_script( 'jquery-ui-datepicker' );
	}

	/*
	 * Two input fields with CSS/JS
	 * If you would like to move CSS and JavaScript to the external file - welcome.
	 */
	function form(){
		
		$from = ( isset( $_GET['mishaDateFrom'] ) && $_GET['mishaDateFrom'] ) ? $_GET['mishaDateFrom'] : '';
		$to = ( isset( $_GET['mishaDateTo'] ) && $_GET['mishaDateTo'] ) ? $_GET['mishaDateTo'] : '';
		
		echo '<style>
		input[name="mishaDateFrom"], input[name="mishaDateTo"]{
			line-height: 28px;
			height: 28px;
			margin: 0;
			width:125px;
		}
		</style>
		
		<input type="text" name="mishaDateFrom" placeholder="Date From" value="' . esc_attr( $from ) . '" />
		<input type="text" name="mishaDateTo" placeholder="Date To" value="' . esc_attr( $to ) . '" />
	
		<script>
		jQuery( function($) {
			var from = $(\'input[name="mishaDateFrom"]\'),
			    to = $(\'input[name="mishaDateTo"]\');

			$( \'input[name="mishaDateFrom"], input[name="mishaDateTo"]\' ).datepicker( {dateFormat : "yy-mm-dd"} );
			// by default, the dates look like this "April 3, 2017"
    			// I decided to make it 2017-04-03 with this parameter datepicker({dateFormat : "yy-mm-dd"});
    
    
    			// the rest part of the script prevents from choosing incorrect date interval
    			from.on( \'change\', function() {
				to.datepicker( \'option\', \'minDate\', from.val() );
			});
				
			to.on( \'change\', function() {
				from.datepicker( \'option\', \'maxDate\', to.val() );
			});
			
		});
		</script>';
		
	}
	
	/*
	 * The main function that actually filters the posts
	 */
	function filterquery( $admin_query ){
		global $pagenow;
		
		if (
			is_admin()
			&& $admin_query->is_main_query()
			// by default filter will be added to all post types, you can operate with $_GET['post_type'] to restrict it for some types
			&& in_array( $pagenow, array( 'edit.php', 'upload.php' ) )
			&& ( ! empty( $_GET['mishaDateFrom'] ) || ! empty( $_GET['mishaDateTo'] ) )
		) {

			$admin_query->set(
				'date_query', // I love date_query appeared in WordPress 3.7!
				array(
					'after' => sanitize_text_field( $_GET['mishaDateFrom'] ), // any strtotime()-acceptable format!
					'before' => sanitize_text_field( $_GET['mishaDateTo'] ),
					'inclusive' => true, // include the selected days as well
					'column'    => 'post_date' // 'post_modified', 'post_date_gmt', 'post_modified_gmt'
				)
			);
			
		}
		
		return $admin_query;
	
	}

}
new mishaDateRange();