Yep, when its trapped in your imagination.

Care to elaborate?

Time is two things.   A means of measurement devised by mankind for keeping track and/or  planning for things, fundamentally based on daily solar cycles, and the relativity of that measurement given the location of mankind to those solar cycles.  Essentially, time is a man-made dimension based soley on the existence of our Sun and the position of the Earth relative to it, and then us, relative to our location on Earth, relative to the Earth's location from the Sun.  Atomic clocks and other devices designed to count resinating particles and vibrations are only a means of exactly that, counting vibrations, with a set start based on again, the Earth and it's position relative to the Sun. For many thousands of years the Earth's position relative to the sun and other stars has remained constant enough to create devices that divide centuries into years into weeks into days into hours into minutes in seconds into nanoseconds.  Its theorized based on applied physics that if a person was able to travel at near the speed of light or faster (~98%) that they could travel through time, but the reality is, through relative time.  For example, if you were to travel at the speed of light for 1 year toward Pluto, and then back 1 year to Earth, essentially you would have leaped forward in time relative to the Earth as relative to the Sun, meaning many hundreds of years would've passed on Earth while you were only gone physically, relative to your travelling device, for 2 years.  So if this were possible, travelling into the future would most likely be possible too.  To travel backward though, its then theorized some sort of rip in the fabric of space is required, such as a wormhole.  Then allowing you to skip going the long way around and just travel from point A to B instantaneously.   In the wormhole case, if found and able to be manipulated safely, travelling both forward and backward in time makes perfect sense since you would be free to move anywhere in the universe at any given time and be there, right away.