danivalentin

This was based on <a href="http://lesterchan.net/wordpress/readme/wp-relativedate.html" title="Relative Date" rel="nofollow ugc">Lester Chan’s Relative Date plugin</a>. 
It tries to simplify things a bit. This plugin can:
<ul>
<li>Replace the_date() in the post</li>
<li>Replace get_comment_date() or comment_date() in the comments</li>
</ul>
Note that if your theme is writing the date in a different form, it won’t work. You have to 
replace its function call to one of the above (in the TwentyTen theme for example, replace twentyten_posted_on() 
by the_date().
Also important to say that, comment replacement won’t work if you are using the default wp comment renderer because 
it calls get_comment_time() as well. You have to do a customized callback function to use with 
wp_list_comments( array( ‘callback’ => ‘your_customized_function_here’ ) ). (ok, maybe things were not 
simplified that much :/)
There is a options page (under settings in the Admin) where you can choose which dates you 
want to replace (posts/comments). Posts date are by default checked.
Portuguese translation included.

Simple Relative Date

A simple way to turn your post/comment date in its relative versions.

Flector

Today-Yesterday Dates is a small, simple plugin that automatically changes the creation dates of posts relative to the current time (only for today and yesterday). In other words, the dates will now look like Today at 11:45 or Yesterday at 9:15.
If a post’s creation date no longer meets the criteria for “Today” or “Yesterday,” the plugin will not change it, and it will be displayed in the default format.
If you liked my plugin, please rate it.

Today-Yesterday Dates

cool :)

This plugin changes the creation dates of posts to relative dates for posts that are dated today or yesterday (relative to the current time, i.e.

Simple Relative Date vs Today-Yesterday Dates