Iconic WDS - Disable ASAP timeslot for other than today's date

functions.php

<?php
// Iconic WDS - Disable ASAP timeslot for other than today's date
function iconic_wds_filter_out_asap_timeslot( $slots, $ymd ) {
	$date_ymd = filter_input( INPUT_POST, 'date', FILTER_SANITIZE_FULL_SPECIAL_CHARS );

	if ( $date_ymd !== wp_date( 'Ymd' ) ) {
		$slots = array_filter( $slots, function( $slot ) {
			return empty( $slot['asap'] );
		} );

		$slots = array_values( $slots );
	}

	return $slots;
}
add_filter( 'iconic_wds_slots_available_on_date', 'iconic_wds_filter_out_asap_timeslot', 10, 2 );