This free WordPress Plugin automatically refreshes Human Readable Time Differences
If your theme shows the date an article was posted in a human readable time difference – such as e.g. “posted 2 mins ago” – this plugin refreshes the time difference once a minute.
On the one hand this is a nice feature for your visitors – and on the other hand this allows you to use a caching plugin! All human readable time differences are updated immediately on page load.
You don’t have to change anything. Just activate this plugin and forget.