While $data["post_time"] is listed as an option for submit_post, it is not used to set the time a post was made.

A minor change at functions_posting.php at line 1638 fixes this:

if ($data["post_time"] != 0)

{ $current_time = $data["post_time"]; }

else

{ $current_time = time(); }

Though the variable should probably be named something other than $current_time throughout submit_post.