How might I format relative dates the way Stack Overflow does "member since" and "last seen"? [duplicate]

This question already has answers here: Closed 11 years ago.

Possible Duplicate:

How do I calculate relative time?

I want to know how to display these data as seen on stackoverflow.com profile page. I have the timestamp of users registered 开发者_C百科date and last visit date. But I need to display using stackoverflow.com format.

For example:

Member since: 9 months

Last seen: just now

Is there any script to convert these dates and display in such format?

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This is a duplicate of this question which is a duplicate of this question which has some great code samples including PHP.

In addition to all this, if are you using jQuery you can do this client-side with something like the timeago plugin. It has the advantage of updating the text as time passes so if you load a page and it says "posted 5 minutes ago" and look again 5 minutes later, it says "posted 10 minutes ago"