Nobody has a good answer.
For classical mechanics, time is the independent variable of any dynamics.
In General Relativity it is like space, one of the dimensions affected by the gravity.
In particle physics time is much more fuzzy concept. For example if we consider an electron moving from the past to the future, we can describe it as a positive electron (a positron) moving from the future to the past. In other words if we switch charge and time we obtain the same equations of motion.
For me what we call tine is an estimation of the entropy. If a process is reversible, the time is not well defined.
But if the process goes from lower probability to higher probability, then you have a past and a future.
For example you can boil an acquarium and make a fish soup, but you cannot take a fish soup and male an acquarium.
But this is my personal opinion, probably every scientist has his own idea about time.
time is fourth dimension - this is too popular on internet .
Time as a function of velocity.
Our calculations with velocity goes smooth until and unless we decide to think about time and since we are too curious to know about it let's talk about it .
As described by the newtonian concept time is absolute or universal everything in the world has same coordinates with respect to the time axis but then came physicist the father of modern physics Albert Einstein
this man was curious to know about whether it's time to understand time it take reference of light when he was young he thought that he will fly on light.
The basic idea of the theory of relativity is that time is not Universal its relative and what makes the time to slow and faster is velocity and gravity.
He derived the formulas of time dilation.
What we generally mean by time is what we see in our clocks but what do these clocks show. We know that the Earth rotates around its axis and revolution of Earth around sun we divided this all occurrence into segments and this is what we call seasons and time.
Let's take an example first for instance let there be a point P in deep space with two neutrinos a and b they both are trouble and the same direction the speed of a is 4 metre per second and b is 2 metre per second so after the interval of 1 second of each of these what will be the distance between the two the answer that we would give to it is 2 metres but this was what Einstein's theory of relativity suggest both neutrinos are not at same time instance when we measure the distance between the two.
So far I haven't written anything about time I've been talking about all the stuff Android that time is function of velocity.
But Time may be real or virtual . But there's something whose effect we do observe in our day to day life . That's what responsible for days and nights .
We have been programmed to accept what's told to us . But may our curiosity doubt the aptness of reality of everything , truly everything .
may the reality not be real.
HOPE IT HELPS