I build quite a few Drupal sites that use embedded YouTube videos, and my module of choice for handling this is Media: YouTube, which is built upon the popular Media module. The Media: YouTube module generally works great; but on one site that I recently built, I discovered one of its shortcomings. It doesn't let you display a YouTube video's duration.

I thought up a quick, performant and relatively easy way to solve this. With just a few snippets of custom code, and the help of the Computed Field module, showing video duration (in hours / minutes / seconds) for a Media: YouTube managed asset, is a walk in the park.