Example of how you can set EE datepicker questions to be readonly which means users must use the datepicker and not type in values manually

tw_ee_datepicker_readonly

<?php // Please do not include the opening PHP tag if you alreayd have one

// Example of how you can set EE datepicker questions to be readonly
// which means users must use the datepicker and not type in values manually.
add_action( 'wp_enqueue_scripts', 'tw_ee_datepicker_readonly', 11 );
function tw_ee_datepicker_readonly() {
    wp_add_inline_script( 
        'single_page_checkout',
        'jQuery(document).ready(function($){
            $(".ee-datepicker-input-dv input").prop("readonly", true);
        });'
    );
}