This is a difficult question to answer in simple terms.
When Newton discovered the theory of gravity and the laws of motion he had to assume that time was fixed and eternal. If you
had a clock and someone on the other side of the universe also had a clock then they would see the same time.
Einstein showed that this is not the case. In his Special Theory of Relativity he showed that time is relative. It depends on
your speed. The faster you travel, the slower time goes. This has been measured, but it is only measured at extreme speeds.
In his General Theory of Relativity he showed that time is also dependant on ones position in space, and that any gravitational
field one happens to be in alters time. This linked Time with space and became the famous space-time continuum.
What difference does this make? Well, it means that because they are linked, Time is just another dimension (obviously the
fourth) and that without space there is no time. This also means that before the Big Bang there was no Time.
What actually
is time though?
We don't know, except that it seems to be a measure of entropy which is a probabalistic term showing the increase in unuseable
energy. That is even more oversimplified than the first bit, but time from a scienticic POV is a useful term which most people
don't think about too much.
Evolution, on many levels, has failed to impress me. This is really not the fault of my mind to comprehend the idealogy
and naturalistic view of Darwinism.
This discussion on Time has nothing to do with Evolution, of course. Time is used within evolution of course but is assumed that the physicists understand it. Biologists do not need to worry about that side.