facetwp date url vars

functions.php

<?php
//load current cw plus 4 weeks on front page date facet
add_filter( 'facetwp_preload_url_vars', function( $url_vars ) {
    if ( '' == FWP()->helper->get_uri() ) {//frontpage
        if ( empty( $url_vars['date_facet'] ) ) {
          $week = date("W");
          $year = date("Y");
          $start_day = date("Y-m-d", strtotime("{$year}-W{$week}-1"));//return monday of this week
          $end_day = date("Y-m-d", strtotime("{$year}-W{$week}-7 +3 weeks")); //return sunday in 4 weeks
          //error_log($start_day);
          $url_vars['date_facet'] = [ $start_day, $end_day ];
        }
    }
    return $url_vars;
} );