Change WooCommerce Checkout Manager Datepicker to Jalali

By looking at the plugin code, you have different options:

Date picker language is being selected based on the following code.

$current_language = ( defined( 'ICL_LANGUAGE_CODE' ) ? ICL_LANGUAGE_CODE : apply_filters( 'wooccm_language_code', false ) );
// DatePicker
wp_enqueue_script( 'jquery-ui-datepicker', array( 'jquery' ) );
if( defined( 'ICL_LANGUAGE_CODE' ) || !empty( $current_language ) ) {
    // Check if WPML is in use or the WordPress Filter has been used
    if(
            (
                    function_exists( 'icl_register_string' ) && 
                    ICL_LANGUAGE_CODE == $current_language && 
                    ICL_LANGUAGE_CODE !== 'en'
            ) || 
            !empty( $current_language )
    ) {
            wp_enqueue_script( 'jquery.ui.datepicker-'.$current_language, plugins_url( 'includes/pickers/di18n/jquery.ui.datepicker-'.$current_language.'.js', WOOCCM_RELPATH ), array( 'jquery' ) );
    }
}

• Define ICL_LANGUAGE_CODE with your required language locale(you can find supported locale here)
• Use wooccm_language_code filter hook if ICL_LANGUAGE_CODE is not defined
• Else dequeue the -fa script and enqueue your own