metaWeblog.editPost changing post time

Regarding metaWeblog.editPost

How do i change the post published date via query string because i know u can edit the post via wordpress dashboard, but i wanna do it in query method like update post meta or something but how do i get about it.

My scenario:

I create a post 7 days ago, 7 days later it was updated and i wanna renew it publish date to the time now. i know i can use time(); to get the time but how do i change the publish post date to the time now by query functions.

Looking forwards for php and wordpress expert for code help.

Thanks,
Baoky