The speed of light is approx. 186,000 mps, and lets say the speed of time is approx. 200 times that.
Now lets say we are standing on a hill, watching the cars on the freeway go by. The cars are going 60mph relative to us, and now lets say we get in our car and travel 30mph down the freeway, the cars are now traveling 30mph relative to us, and if we speed up to 60mph, they would be going 0mph relative to us, and if we go 120mph, they would be going backwards 60mph relative to us.
Use this same concept for time, here we are on earth watching time go by at its normal speed. however, if we decide to go half the speed of time, (100 times the speed of light) time would only be moving half as fast relative to us, and if we go the speed of time, time would appear to be frozen relative to us. And if we go twice the speed of time, (400 times the speed of light) time would go backwards relative to us.
However, if you go faster than time, how can time exist for you? In other words, lets say you wanted to go 5 years back in time, you could go twice the speed of time for five years, or go several hundred times the speed of time for an even shorter ammount of time, except, how can there be time if your going faster than it? So, there would be no way to decide how far back you go? Or what would happen?
Also, you could say that time is going back, relative to you. Which I belive would mean that you would de age, and also loose memories, IE. be exactly as you were at a previous state. So, once memories and all that could be transfered, I suppose this could be used as a 'fountain of youth' except by the time we are able to go faster than time, aging will prob already have been solved some other way.
Now, for going into the future...
Well, according to Einsteins theory of relativity, it is possible to travel into the future, except it's not really traveling into the future, but speeding up time for others.
The way I see it is, the future hasn't happened yet, so the only way to go into the future, is to wait until it happens. So, technically, we are already traveling into the future. But, if you want to 'travel' 1 million years into the future, you'd have to freeze yourself.
Lets say absolute zero is real, and is achievable. When an object (human) reaches absulute zero, it's molecules would freeze and stop vibrating, when they vibrate alot, they are a gas, when they vibrate a little, a solid, but when they don't vibrate at all, they are only molecules. And molecules can't age, or die. So, a million years could pass bye, and you heat up the molecules and let them start vibrating again, it would only appear that a second has passed by, when really it was a million years, thus 'traveling into the future'.
So, we're still far away from achieving any of this, but it could be possible?