Today, my friend called me to go watch a movie: "The day after tomorrow"....i wanted very much to go but happened to be not able to make it in time......which sets me thinking, what's time?

Time, as defined in dictionary: "the continuum of experience in which events pass from the future through the present to the past". It is a measure of the experience we went through or the events that happened. Let's say, from a coma patien's point of view, time is simply the period of events he experience from his birth from the moment he is in coma, for when he wakes up, his memory would only continue from that point, he may be phyically 30 yrs old but his mind is only that of 15 or at whatever moment he hits coma.
Time is relative, according to Einstein, and whatever is relative is just as inaccurate as its referral, lets say if time stops now for the world, except for one person, for about 2 years, everything is in a standstill, including celestrial movements, then when time reverts back, the whole world would have thought that nothing happened, except for the one person that has experience it. Time, to the world, is just as normal and moves on like it should be. You may want to question, how could the time just stopped? It is said that during an absolute zero, a temperature of -273 deg Celsius, everything would have stopped moving, including atoms and the electron obiting them, everything would have freezed and without doubt, the universe would too. The big bang had managed to keep most of the universe approximately 3 deg above Kelvin, but how do we know if when or where are we hit by absolute zero? Time, in that case, dosen't seemed to be moving.

By scientific theories, time is like a line, and it bends around bodies of great masses, like the planets. This line connects the entire universe, but a singularity (black hole) would break this line, and could join it back with any other part of the line, thus creating a theory of "time travel". Yes, in theory we could do that, not only can we determine when we want to come out, but also where. But then again, we have not found a way in which we could go into a singularity safely. So time seems quite boring for us to talk about at the moment. Can we control time? Can we travel through it, or can we bent it to suit our needs? Only time will tell.

"When you have passed a stage of your life, don't stop to look back, time does not wait for you, yet."