Time snag

I am very much interested in concepts that deal with time, time travel and time dilation. When working on different equations that relate to time, distance, speed and various other mathematical equations, I arrived at a conclusion that the amount of aging of a living thing happens at a slower rate when that living thing is travelling along with time. This in similar to the twin paradox concept wherein a person constantly in motion with time tends to age slower than the one who is not so constantly in motion with time. Now this gave me a better idea about time travel and why people say time travel to the future is possible but not the past.