Time travel to the future is definitely possible due to the ‘time dilation’ effect when travelling close to the speed of light.
For someone travelling close to the speed of light, time slows – the closer to the speed of light, the greater the effect.
So it is not science fiction that two twins (born at the same time), one placed in a spaceship travelling the universe at close to the speed of light – could return to earth at say aged 10, to find their twin living on earth to be over 80 years of age.
By travelling very close to the speed of light, it is possible to travel 100s if not 1,000s of years into the future.