On Facebook, each comment or other user event has a timestamp. But it is not listed as a simple date, but presented in a form of a human-friendly string. For example if right now it is 08:38 and the comment was made at 08:31, Facebook doesn’t just tell you the time, but says “7 minutes ago”.
Is there an open source implementation of Facebook algorithm (or similar) that takes a data of event, a current date and tells in a human-friendly form how long has it been since?
You could dig into timeago jQuery plugin’s source code to study.