App submission response: "Post-dated Code Signature"
Seems straightforward enough, the app you uploaded has a timestamp that indicates your machines time is incorrect (namely according to the stamps it was built after you submitted it), so either you have a time machine, or just the wrong time set.  They are just letting you know, and allowing you the chance to correct the issue and resubmit if you like.  It doesn't read as a rejection to me.