For example, if your site URL contains this query string:
https://www.yoursite.com?theyear=2019

Add the following PHP code to your child theme functions.php file.

[php]
// look for parameter in URL for year and add the class customHide
if (isset($_GET['theyear'])) {
  $theyear = $_GET['theyear'];
    if ($theyear = '2019') {
  // Add specific CSS class by filter. 
    add_filter( 'body_class', function( $classes ) {
        return array_merge( $classes, array( 'customHide' ) );
    } );
    }
} else {
  //Handle the case where there is no parameter
  // Add the class customHideTwo
    add_filter( 'body_class', function( $classes ) {
        return array_merge( $classes, array( 'customHideTwo' ) );
    } );
}
[/php]