Modify format of the selected date at Reservation Table.

wds-reservation-table-change-date-format.php

<?php 
/**
 * Modify format of the selected date at Reservation Table. 
 * Remove st, th, etc suffix.
 *
 * @param array $dates Dates.
 */
function iconic_wds_modify_date_format_reservation_table( $dates, $format ) {
	if ( ! wp_doing_ajax() ) {
		return $dates;
	}

	if ( 'array' !== $format ) {
		return $dates;
	}

	foreach ( $dates as &$date ) {
		$date['formatted'] = date_i18n( 'D, j M', $date['timestamp'] );
	}

	return $dates;
}
add_action( 'iconic_wds_available_dates', 'iconic_wds_modify_date_format_reservation_table', 10, 2 );