According to Albert Einstein.for us physicists believe the separation between past, present, and future is only an illusion, although a convincing one. which refers that division of present, past and future all are illusion. Although, it was not possible for Albert Einstein to relate present, past or future neither he could understand the separation in between them as well. So what do you think? Its not possible to define time? Lets see the definition of time in this book and check out the relations between past, present and future with mathematical formula also. After reading the whole thing you will get the proof that Mr. Albert Einstein is not correct now anymore and present is equal to the summation of past and future although that has no value for human and this is the present that had been referred as the earth life or the life of world; meant by the prophets and religious people. Actually, Theory of relativity of time - relation between past, present and future will show you that present becomes a fact or reality in 0 zero hour. And the universal constant for time is Pr=0.