add-field-on-delievery-date-field-oncheckout.php

<?php

/*
Plugin Name: Add Fields on WooCommerce checkout page.
Description: A simple demo plugin on how to add add extra fields on WooCommerce checkout page.
Author: Bhavik Kiri
Version: 1.0
*/

add_action( 'woocommerce_after_checkout_billing_form', 'display_extra_fields_after_billing_address' , 10, 1 );

function display_extra_fields_after_billing_address () {

     _e( "Delivery Date: ", "add_extra_fields");
     ?>
     <br>
     <input type="text" name="add_delivery_date" class="add_delivery_date" placeholder="Delivery Date">
     <script>
         jQuery(document).ready(function($) {
	      $(".add_delivery_date").datepicker({
	          minDate: 0,	
	      });
          });
      </script>
     <?php 
}

add_action( 'wp_enqueue_scripts', 'enqueue_datepicker' );

function enqueue_datepicker() {
    if ( is_checkout() ) {
        // Load the datepicker script (pre-registered in WordPress).
        wp_enqueue_script( 'jquery-ui-datepicker' );

        // You need styling for the datepicker. For simplicity I've linked to Google's hosted jQuery UI CSS.
        wp_register_style( 'jquery-ui', '//code.jquery.com/ui/1.11.2/themes/smoothness/jquery-ui.css' );
        wp_enqueue_style( 'jquery-ui' );  
    }
}

add_action( 'woocommerce_checkout_update_order_meta', 'add_order_delivery_date_to_order' , 10, 1);

function add_order_delivery_date_to_order ( $order_id ) {
     if ( isset( $_POST ['add_delivery_date'] ) &&  '' != $_POST ['add_delivery_date'] ) {
         add_post_meta( $order_id, '_delivery_date',  sanitize_text_field( $_POST ['add_delivery_date'] ) );
     }
}

add_filter( 'woocommerce_email_order_meta_fields', 'add_delivery_date_to_emails' , 10, 3 );

function add_delivery_date_to_emails ( $fields, $sent_to_admin, $order ) {
    if( version_compare( get_option( 'woocommerce_version' ), '3.0.0', ">=" ) ) {            
        $order_id = $order->get_id();
    } else {
        $order_id = $order->id;
    }

    $delivery_date = get_post_meta( $order_id, '_delivery_date', true );

    if ( '' != $delivery_date ) {
        $fields[ 'Delivery Date' ] = array(
	    'label' => __( 'Delivery Date', 'add_extra_fields' ),
	    'value' => $delivery_date,
        );
     }
    return $fields;
}

add_filter( 'woocommerce_order_details_after_order_table', 'add_delivery_date_to_order_received_page', 10 , 1 );

function add_delivery_date_to_order_received_page ( $order ) {
    if( version_compare( get_option( 'woocommerce_version' ), '3.0.0', ">=" ) ) {            
        $order_id = $order->get_id();
    } else {
        $order_id = $order->id;
    }

    $delivery_date = get_post_meta( $order_id, '_delivery_date', true );
    
    if ( '' != $delivery_date ) {
    	echo '<p><strong>' . __( 'Delivery Date', 'add_extra_fields' ) . ':</strong> ' . $delivery_date;
    }
}