How can I change the date of a thread or a post?

[Ark del KAOS]

I'll try to explain myself the best I can ^ ^
When you send a new thread/post, it get in its information the date of when you send it. Month-Day-Year, Hour-Minute-Second.
The oldest, the first.
And that date looks to be unchangable. I cannot change a thread/post date to make it older or younger.
I need to be able to change that. Is so useful!
If I can change the date, I can make a new first post for the thread, and take de ownership. Or in my VBAdvanced, I can send a old news thread again to the top of the news module.
It's there a existing mod already?
Thanks!