Well now thats a really good question, I really don't know how to answer it to tell you the truth.

A more interesting question would be is...

If you go in the past and do either rape or fuck yourself, it considered sex or masterbation?

My brain hurts now.

hmm.... It also depends on how much information you can give. if you can tell and convince the other time person that its actually you from the past/future, then all is well. if you can't then there are still choices available. if you go into the past, that's pretty much it, since there's no way they could know you from then. if its the future you're heading for, however, then its possible even without telling, as the spouse may be able to recognize the younger you. if you went back to when they were with someone else, the yes, it would be cheating, as for the fact that since they don't know the future like you do, they won't know for sure that they aren't going to stay together (your spouse and the other guy). the real question, it seems, is that if you went back and did your spouse, would that change time and make it so that you're no longer together with them? and if time chances so that your no longer with them, that would mean that you'd be with someone else. and since you're with someone else, you would have no memory of being with the first person you were with. and what if the person you were with in the first place was the ONLY reason you went back in time? That would mean that you would suddenly find yourself back in time, screwing some woman you don't know, with no memories as to WHY you're there in the first place.

Hows that for in-depth?

My head hurts, Cellidor...

and that's what we have these things for *hands over a piece of pie with ice cream on it, a refreshing beverage, and a porno*

*noms, slurps, and faps*

Better question. If you had sex with yourself, would it be gay or masturbation?

Neither. It would be AWESOME.