gistfile1.txt

add_action('wp_enqueue_scripts', function() {

    wp_enqueue_script('jquery-ui-datepicker');

    $custom_js = "
        jQuery(function($){
			if ($.datepicker && typeof $.datepicker.setDefaults === 'function') {
				$.datepicker.setDefaults({
					dayNamesMin: ['S','M','T','W','T','F','S']
				});
			}
        });
    ";

    wp_add_inline_script('jquery-ui-datepicker', $custom_js);
}, PHP_INT_MAX);