My morning coffee has kicked up three answers in my head:
Firstly, god could've existed in time, with there being an infinite span of time before he created everything else with none but himself to motivate himself to decide on doing anything.
Next, god might've created time with everything else, in which case god somehow changed what it was or was not doing over no span of time.
Or lastly, god might just BE time, like some pagan father time or something. I can't even posit a guess as to what that would or would not allow.
If God existed, it follows that everything, including time was created. If he doesn't exist, time still does.
Time only moves in one direction that we perceive, regardless of Daylight Savings. We have no way to restore the universe to an earlier state, although we can observe that earlier state by moving farther away, we can't change what happened.
If you are a christian, then of course it invented time. It created everything.
What I usually ask christians is what the hell was he doing before he created life, the universe and everything?
Was he playing scrabble with Zues for eternity? Remember he was around for eternity before he made us - were we a way to relieve his boredom? Maybe he just had wind and we were an accident.
He certainly had enough time to make a better job than he did.
I would say that time would have began when God did. If there is no beginning of god, then time must be infinant. Existence requires the passing of time. Meaning anything that exists must at minimum occupy a space in time. Even thoughts are dependent upon time.