The subject of time fascinates me. The human describes time for the most part in manmade measurements of years, days, hours, seconds. The fact that these are linked to the rotation of the Earth is immaterial. That is a measurement of convenience, nothing more. However, our perception of time would seem to be related to the heartbeat.
If you look at small animals with a short lifespan in human terms, take a mouse for example, they have a rapid heartbeat, and seem to scuttle along and perform their daily tasks with lightning speed. When a mouse runs across your path, his legs seem to work at an impossibly fast rate. To a mouse, the world probably appears much as it does to a human, and humans probably appear as huge, very slow, lumbering beasts.
Conversely, long lived animals with slow heartbeats, such as elephants and tortoises, probably perceive humans as scuttling around too fast, much as we perceive mice. Picture an old Buster Keaton movie reel played at fast speed, with the actors scuttling about everywhere much too fast.
Taking this into account, while it is very easy to think back to what the world was like a couple of years ago, and what we were doing at any given time in our lives, it is very hard for a human to perceive the vast timescales of prehistory. The dinosaurs died out 65 million years ago. It is impossible for the human brain to quantify that in relation to our own puny lifespan.
On a universal scale, if there were a greater consciousness capable of it's consideration, then the billions of years of the Earth's formation and the evolution of life, would probably appear to happen unimaginably quicker than the human brain is capable of doing. A single lifespan, or even the whole history of humanity, would be no more than a bubble appearing in a test tube and popping almost immediately out of existence.
Conversely again, on the atomic level, there could be a whole universe of life and interaction happening in the time it takes a human to blink an eyelid.
We are constrained by an unwritten law, which would seem to allow us only to perceive whatever is within our heartbeat's ability to perceive, on a human scale. That which is eons greater, or ions smaller, is outside of that, and can only be related in mathematical equations, but not in terms of human perception or experience.
Personally I think time is more of a pyschological construct than a real thing in and of itself.