Showing thread/post age rather than date?

[ArgylePhoto]

Hi,

In one of my forums I'd like to display the age of a thread rather than the date it was created on, is there any easy way to do that?

Specifically the forum is filled with one-post threads (for sale adverts) and on the threadbit template I have the date of the last post (which is obviously the original post) showing just as 'dd/mm/yyyy' with no other info, but I'd like to change that to an advert age like 'xx days'. I'd also like to have that info in the showthread template too instead of a date.

Thanks in advance