I was surprised when Professor Block said that science had not been able to define Time. I had once (AS A TEENAGER) offered my own definition as follows:
"Time is the movement of moments."
Given Hawkin's explanation on the same question, I was uncannily close.
Let me offer a mathetical formula then for what I believe to be the 'definition' of time:
If X = any agent/permutation of change (ie an infinite number of possibilities) and T = a singularity (a moment in Time) then
Time = XT or
T = Xt
Thus the particular moment in time in which the 'Now' is experienced, or the 'continuous moment of creation' can be defined as the convergence/correspondence of a moment to the experiential permutation of it.
Mathematically this correspondence (the experience of 'being in the moment at a moment's notice': if x= 1 and t = 1 then Xt = 1 (1=1)
There are naturally other dimensions of the now (2=2; 23756 = 23756) etc, but of course all of these are vastly outnumbered by 'relative time' (the past/the experience of one part of space being out of sync (not correlated/moving away and out of touch) in terms of light (and the view or experience of distant reality) not having reached there.
Semantically the definition of time is quite simple, but nevertheless profound.
Time is Infinite Possibility.
Note that time is a state, more closely allied with where, than when. When is always relative and loses sight of where. Without where (a point in space), when (something relative to something past or present or future) makes plenty of assumptions.
This postulation includes that in each moment there are infinite possibilities for infinite possibilities. Which is a thrilling thought if we choose to seize the moment in act of decisive, strategic, logical activity.
The measurement of time is so critical to the functioning of modern societies that it is coordinated at an international level. The basis for scientific time is a continuous count of seconds based on atomic clocks around the world,
Since January 1, 1972, it has been defined to follow TAI