FacetWP – force date picker range

<?php

// Add to your (child) theme's functions.php
// replace "YOUR_FACET_NAME" with your *actual* facet name

add_filter( 'facetwp_render_output', function( $output ) {
    $output['settings']['YOUR_FACET_NAME']['range']['min']['minDate'] = '2021-03-21';
    $output['settings']['YOUR_FACET_NAME']['range']['min']['maxDate'] = '2021-12-31';
    return $output;
});