"What is time?" That is a good question.
All things in this universe have a rhythm or a change that is like a rhythm. What is a rhythm? It is a repeating cycle that contains a start, change in state and a stop were it then repeats with a new start.
Anything in this universe can be broken down into this rhythm and rhythms containing parts that are in rhythms. But remember that time is a change. It is the number of rhythms that determines the rate of change. It is the amount of change that determines time. If something has little change, than it has little time.
So that you can understand this, an example is a person that is slow verses a person that is fast. One got more done at the end of the day. Thus one had more time. But both got to the end of the day.
Some people have referred to time as an illusion for this reason. Both people in the above example will have made it to the end of the day. It was the same day. But still, one got more done thus he had more time. So time is relative. The amount of change that occurred is the amount of time that past for that thing or rhythm.
At one end of a scale is no time, where there is no change. At the other end is the illusion of a high rate of change and thus lots of time.
You can see this in Physics, make something cold and it slows and often last longer, heat it up and it speeds up and is gone faster simply by changing.
If you use a clock, it has a steady rate of change, thus it has the same amount of time from moment to moment and time does not speed up nor slow down. And in fact a clock is judged mainly by how constant it's change will be. The relativity of time requires us to use constants so that we can agree on how much time has past and not get lost in all this relativity. If the Earth ran by your relativity, we would have long days and short days based on your speed of rhythm cycles.
That we use the cycles of the Earth to refer to time and think all things have had the same amount of time is the illusion. The passage of time was relative. Just because one person moved faster and got more done does not mean he will age faster than the other guy, as that is measured by his body, not how fast he ran. As rhythms are all over the place and we need a point of reference to stay in sync. And the body has found something to judge it's rhythms so you can tear it up by being in a hurry and not get older. But speed it up, or slow it down beyond the rhythms it has to work with, like the heart or time for chemical changes, and it will die. Go too slow at work and it will not make enough money or change fast enough to survive.
Thus time is a state of change that all things have. And thus time is judged by relative difference in two or more rhythm cycles. Such as: In one day, I got twice as much done, is the same as, I had twice the amount of time.
The idea that moving at the speed of light will change this is false if it does not affect the speed of a rhythm's cycles. You can go a thousand times the speed of light and still pace out the same amount of time with the same number of rhythm cycles. And the idea that time is out of your control is the product of people that forget that time is relative to the speed you finish rhythms and the illusion that all things have the sames passage of time. The passage of time is not the same for you and me in a day, year, decade, millennium, etc,... The true concept of time runs head long into the illusion that all things have the same amount of time, a factor that has been ingrained into people and so may be hard for some to grasp.
If you understand what I have written then you will understand time, there is no other factor to time that dictates it's passing. Apart from rhythms, speed and time are disrelated. The overall passage of time is the illusion created by all the change that has occurred. If you look at the change that has occurred for any object, you will see the amount of time that has past for that object. That we us the Earth is just a standard, so that we can all get along in all this mind boggling amount of relativity. If anything ever had absolutely no change, by the rules of this universe, it would have no time, it would no linger persist and would vanish, never to be seen or have any influence ever again.
At this point I as you to look at your own life to see how time passes. The feeling that time has rushed by while you were busy doing something is the perception that occurs when you speed up the rhythms of your life. The feeling that time is moving slow is the perception that you get when you sit still doing just about nothing. "Some people are always in a hurry" is the same as "Some people make more time with a rapid standard of relativity (or a higher speed of rhythm completion)".