Automatic cache busting in the Genesis Framework based on the last time the file was modified.

auto-genesis-cache-busting.php

<?php
// Remove the default Genesis child theme CSS
remove_action( 'genesis_meta', 'genesis_load_stylesheet' );
add_action( 'wp_enqueue_scripts', 'prefix_load_stylesheet' );
/**
 * Get the time the theme's CSS was last modified
 * and use it to bust the cache by appending
 * it to the CSS output.
 *
 * @author FAT Media
 * @link http://youneedfat.com
 */
function prefix_load_stylesheet() {
	// Get the stylesheet info.
	$stylesheet_uri = get_stylesheet_directory_uri() . '/style.css';
	$stylesheet_dir = get_stylesheet_directory() . '/style.css';
	$last_modified = date ( "h.i.s", filemtime( $stylesheet_dir ) );

	// Enqueue the stylesheet.
	wp_enqueue_style( 'prefix-styles', $stylesheet_uri, array(), $last_modified );
}