Určitě jste narazili na údaje o čase jako „Publikováno před 4 hodinami” apod. jQuery plugin timeago vám takovou časovou známku vygeneruje nějak takhle:

jQuery(document).ready(function() {

Vygeneruje třeba…

<abbr class="timeago" title="July 17, 2008">3 years ago</abbr>

Ale funguje i takhle

jQuery.timeago(new Date());             //=> "less than a minute ago"
jQuery.timeago("2008-07-17");           //=> "3 years ago"
jQuery.timeago(jQuery("abbr#some_id")); //=> "3 years ago"     // [title="2008-07-20"]

Podporuje českou lokalizaci.

Díky @daeltar

0.1 second is the response time limit if you want users to feel like their actions are directly causing something to happen on the screen. For example, if you click on an expandable menu and see the expanded version in less than 0.1 seconds, then it feels as if you made the menu open up. If it takes longer than 0.1 seconds for the revised state to appear, then the response doesn’t feel „instantaneous“ — instead, it feels as if the computer is doing something to make the menu open.

Celý článek na usetit.com