As userscripts.org is down, so goeth my documentation. Off the top of my head, the following code is for the Penny-Arcade forums, and has two functions:
First, while the time and date is found within the source for each post, by default it only displays the time (on a recent post), or day (if the post was yesterday or older), or if the post is old enough only the month the post occurred in. This replaces that display with the full time and date from the source.
Second, this adds the post count, there's some hacky replacement that goes on because the first post in a thread starts at 1, and the second post in a thread starts with 2... so maths are done to correct that.