I realise that time-'speed' is the same as light-speed as in Astrophysics and Relativity.
However, that time 'speed' refers to a different 'speed'. When I wrote Time-Speed in my previous message, it meant the speed of time in the very common way. One single day means one full rotation of Earth on itself (24 hours). One single day maybe of 16 hours only in another planet. Hence, Time does not have speed! It depends which planet you live on. In another word, PEOPLE INVENTED THAT ONE SINGLE DAY SHOULD BE EQUAL TO ONE ROTATION OF A PLANET ON ITSELF. If I were able to come back somewhere in the past and told people there that ONE DAY IS EQUAL TO FIVE ROTATIONS OF EARTH, you then would in the time being say that one single day equals 120 hours, right? The 'Term' 'Time' did not come out itself naturally. Human beings invented that one single day should equal one rotation of a planet on itself.
With the idea, you may be able to faster the Earth rotation on itself in order to get into future but still, the date maybe different but you are neither older nor younger. But I do not think this idea will work.