Displaying Relative dates is a thing that you often see in Social Media sites like Digg where it says submitted 23 mins ago. A similar concept can be used for Blog posts and comments in WordPress where you can display relative dates as timestamps. This is a good plugin to use in the comments because it helps interaction and shows activity within the blog.
Example of Post/Comment Date and Time
10th January 2007 (2 days ago)
25th January 2007 (2 weeks ago)
21:10 (2 seconds ago)
21:15 (5 minutes ago)
22:15 (2 hours ago)
Find a similar code in your single.php, index.php, comments.php and page.php
<?php the_date(); ?>
Replace it with:
<?php relative_post_the_date(); ?>
Note: You do not have to update all those files, only update the ones that you like, but those are some that might be needed.