however you can not measure any other dimension. How do you measure the first, second, or third dimension? That just doesn't make sense.
PM8228 being as the first 3 dimensions are length, width and height yes you can measure them - they are the common dimensions that partly make up our physical universe. However things like the units of measurement e.g. metres, inches cubits etc are purely man made derivations so that we can say that a plank of wood is X by Y by Z inches. Similarly the measurements of time are man made derivations so that we can say an event lasts for 24 seconds or whatever. The most 'accurate' time in common use at the moment is based on atomic time which is based on counting cycles of an electrical signal resonating with an atomic transition state i.e. an electron flipping between energy shells. The definition of atomic time from here is

The second is the duration of 9,192, 631, 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.

The thing to remember is that although units of time are man made that does not mean that the phenomenon they measure is not real - like Moonwolf says
you cannot go around the fact that what I did (insert time measurement here) ago happend in the past. I can not do that ever again in exactly the same way with every molecule in the positsion as it was then
(actually as a side note that would bring about an interesting philosophical question - suppose you did go back in time in order to change a future event in your own personal history and all of the molecules were in exactly the same place - would you end up doing the same thing as you previously did? The answer is probably not since the you that went back is not the same you that existed in the original time frame)

time itself is a dimension like the other 3 (l, w, h). We have the capability to percieve 3 dimensions fairly readily but apparently we can't percieve the fourth i.e. time dimension very well. You don't need a scientist to tell you that what I am typing on i.e. a keyboard has some physical prescence (because of its physical dimensions) and that in all probability it will still exist tomorrow (drawing on past experience). Hence my memory and experience lets me know there is a before and after the present 'now' i.e. time and there is something I can touch.

PM8228, out of curiosity why do you say

was forced to work by inventing other things leading ultimately to Quantum physics which can not really be proved either way, so scientists assume it is true because it makes everything work.
as someone with a reasonably advanced scientific background I could say that certain things about quantum physics have been proved true - but I'm not going to. The reason I'm not going to is because I have seen enough inaccuracies in scientific papers and incomplete or incorrect conclusions drawn from somewhat 'dodgy' data to be slightly cynical about science. Don't take that as me saying I will believe any 'new age' or religious theory because I don't. I will say that neither religion or science (as it is currently practiced) will lead to 'truth' at best its a case of the half blind leading the blind.

Z