There are many philosophies that can explain this. The one I agree with the most is that of a loop. It's a circle. It has no end or beginning, but also, it has no finite length. Now one might argue that the circumference of a circle can be quantified, but well that comes from our assumption of "units". And these "units" make all the difference.

Keep zooming in on a line and it keeps getting bigger. As soon as there is a gap between two points, there is another point to fill that gap, as a line by definition is a collection of points adjacent to each other. Don't think too hard about the meaning of adjacent, language's affect on perception is a different ball game altogether.
A circle is no different, its simply a curved line.

Now how much you wanna "zoom" defines the speed at which you process and hence perceive things. Think of it this way. Say you're in a garden. And it's the fall season. And say you've never experienced falling leaves before. You'll notice some leaves reach the ground sooner than other ones. And as soon as the fastest leaf hits the ground, that completes your first experience of watching a leaf fall. Say it had been a different leaf, a different tree, and you would've taken longer to complete that experience. Sure, you may notice something different about a slower leaf, perhaps its trajectory, perhaps its rotation, but that is exactly the point. Its about what you focus on. It's how you make up your own "units".

Time is independent of all species. Because all species have a different version of time. Even different people have different versions of time but that is again a different topic. Time will never end, because it never began. Because in order to begin, there needs to be an event or a process that triggers it. Any process has inputs and outputs. So what were the inputs of the first process ever? If you say "nothing" well then how did you work on "nothing" to create "something"? That contradicts the very assumption of start, end and processes.

It's misleading to say that time "was" or that time "will be". Time simply is. And we are here to experience it in our own unique, small way.