What Is Time

I have been thinking a lot about this question lately. What exactly is time. Is it just a human notion that doesn't really exist? Is it linear? The answer is very elusive.

But I think I came up with an answer that satisfies me.

Time, is motion. Without motion there is no sense of time. Think about. In the movies, when somebody stops time, what else stops? All motion. How do we tell time? By the motion of little quartz crystals, or the movement of the sun.

Time = motion, without one there is no other.