Here I'll show you how to find old posts by a specific person.
First, open the search thingy on the forum (duh).
Then, type in this phrase.
That'll show you posts that I posted before December! You can change it to different users and months, also. You can even put a specific date instead of a month!
You can also use other phrases. An example is:
before:December after:October user:CreativeCoder
This will show you posts that I posted between October and December.
There are many other phrases you can use. A way to see all of them is to follow these steps:
1) Open the search.
2) Click the tiny aqua "options" button in the corner.
I hope you can use this small trick with the forum search.