Could a white hole used in conjunction with a black hole be used for time travel?

I assume by 'time travel' that you mean getting from one part of the universe to another part of the universe in a time period that is shorter than if you were to travel that distance at near the speed of light. So called 'hyperspeed' or 'travel through hyperspace'. I make that assumption in order to distinguish from the day to day time travel which occurs routinely every time we move away from a stationary observer and return to that observer some time later, arriving back into his or her future although our clocks would tell us otherwise. But that's another subject.
So if my assumption on your definition of time travel is correct, my answer is as follows:
First, black holes , which absorb mass, have been proven to exist; white holes (mass emitters), have not. But if white holes are one day found ..and there are those who already believe that our universe is a white hole having evolved from the explosion of a super super super mother black hole at the 'Big Bang' some 13 billion years ago, what would happen at the black/white hole conjunction is not travel through time, but, rather, travel to another universe, or, at least, to a higher order dimension of space time! Unfortunately, if I understand Hawking correctly, it appears that only ultra short length, ultra high frequency gravity waves, such as may exist in black holes, would be capable of making this passage. You and I, mere mortals, are forever confined to our 4D universe, and there is no way out. So in summary, the answer to your question is 'no'. Time travel, if it ever becomes possible, must be not via black holes or white holes, but wormholes (q.v.)

Gerry,

Assuming that you could survive the trip which is a real stretch of imagination (pun intended), after reaching the new universe via a white hole, go to the nearest black hole and return to our universe. Problem is, you wouldn't know how far away you are from your starting point. And the only way back would be to retrace your steps. And I don't think that there would be any benefit in taking the journey in the first place, unless you could bring back some knowledge that you have gained. I started pondering this theory about ten years ago. Unfortunately, I haven't been reading much science since then and am not very informed. Got any good reference on worm holes? Good talking to you.

Edgeview A.K.A. Trueview

The best reference that I am aware of on time travel through wormholes or dimensional travel through black holes can be found in Hawking's book which came out 2 or 3 yeras ago entitled 'The Universe in a Nutshell'. Ever since the collapse of Ask Jeeve's Answerpoint, where questions such as yours were a daily rather than a yearly event, I too have been a bit out of touch with the latest scientific advances. Thanks for reviving my interest. If I recall, travel through wormholes is one way only, you could never retirn from whence you came. I see no reason, however, why dimensional travel through black holes couldn't be a round tripper, but I don't know where you'd end up upon returning. Take care.