Enables the %monthcode% and %monthname% tag for permalinks in WordPress.

monthname.php

<?php
/**
 * Plugin Name: Month Name
 * Description: Enables the <code>%monthcode%</code> and <code>%monthname%</code> tag for Permalinks.
 * Author: Roger Chen
 * License: GPLv2
 */

/**
 * Enables use of monthname (january, june) and monthcode (jan, jun).
 * Supports permalinks in the form of /2016-nov/61742/..slug.. or /2016-november/61742/..slug..
 */
class MonthName {

	/**
	 * Month Names
	 */
	public static $monthnames = array(
		'january',
		'february',
		'march',
		'april',
		'may',
		'june',
		'july',
		'august',
		'september',
		'october',
		'november',
		'december',
	);

	/**
	 * Month Codes
	 */
	public static $monthcodes = array(
		'jan',
		'feb',
		'mar',
		'apr',
		'may',
		'jun',
		'jul',
		'aug',
		'sep',
		'oct',
		'nov',
		'dec',
	);

	/**
	 * Registers all required hooks
	 */
	public static function init() {
		add_rewrite_tag( '%monthname%', '(' . implode('|', self::$monthnames) . ')' );
		add_rewrite_tag( '%monthcode%', '(' . implode('|', self::$monthcodes) . ')' );
		add_rewrite_rule(
			'^([0-9]{4})-(' . implode( '|', self::$monthnames ) . ')/([0-9]+)/?',
			'index.php?p=$matches[3]',
			'top'
		);
		add_rewrite_rule(
			'^([0-9]{4})-(' . implode( '|', self::$monthcodes ) . ')/([0-9]+)/?',
			'index.php?p=$matches[3]',
			'top'
		);
	}
	/**
	 * Filters the month name and month code tags
	 */
	public static function filter_post_link( $permalink, $post ) {
		if ( false === strpos( $permalink, '%monthname%' ) && false === strpos( $permalink, '%monthcode%' ) ) {
			return $permalink;
		}

		try {
			$monthindex = intval(get_post_time( 'n', "GMT" == false, $post->ID ));

			$monthname = self::$monthnames[$monthindex - 1];
			$monthcode = self::$monthcodes[$monthindex - 1];
			
			$permalink = str_replace( '%monthname%', $monthname, $permalink );
			$permalink = str_replace( '%monthcode%', $monthcode, $permalink );

			return $permalink;
		} catch (Exception $e) {
			return $permalink;
		}
	}
	
}

add_action( 'init', array( 'MonthName', 'init' ) );
add_filter( 'post_link', array( 'MonthName', 'filter_post_link' ), 10, 2 );

It will work with post_id but not post_name. Can you please say how to make it work with post_name.