Why we do not have time machine yet

I am coding the AJAX web framework that I created two years ago. It is so inconvenient that I want to go back in time and kill myself for it (even though it was my first AJAX framework).

In my perception either (A) our environment (god, nature, emulator, whatever...) prevents inventing of time machine for some reason or (B) such invention allows future people to travel back in time and prevent such invention for some nasty reason thus closing the timeline loop.

Considering "The Matrix" theory of emulation our universe exposes no API to reconstruct its past state or perform other versioning operations like branch and merge. No guarantee that our emulator even uses versioning internally.