If you and I were to get on a space voyaging ship and accelerate to 99% the speed of light at a constant 32 ft/s, G, then in 1 year we would have traveled roughly half a light year. For 10 years we stay at this constant velocity. We begin slowing down which takes another year and half a light year. Another year and half an light year later we're heading back to earth at 99% the speed of light once again. Another 10 years flies by and then you begin slowing down again to final come back to home.
I can't quite remember, I couldn't find any definite numbers anywhere other than the lorentz factor (http://en.wikipedia.org/wiki/File:Lorentz_factor.svg) that basically shows that as you approach the speed of light your time dilation is vastly increased. All this is to say is that the amount of time passing for you relative to someone on earth would become distorted to where for every second you felt 5 seconds, 2 minutes, or an hour, could have passed back on earth. So that after we took our 24 year long trip we would come back to earth having only aged 24 years while the earth had for hundreds perhaps.
And even if it were only twice as long what we put into it it would be quite incredible to have traveled into he future.
