It is the nature of that physical entity we propose to explore. Time, like energy, is found in photons. Time photons, which we are calling tymitons, like energy photons, have definition without physical boundaries. Time, like energy, has a mass equivalent. Time is the ocean of our universe.
Matter protrudes into time.
The protrusion of matter into time, is a state of dynamic balance between forces. One way matter interacts with time is by friction. Time in our universe, like the oceans here on earth, differs from one place to another. As our ocean is essentially water and water everywhere, although the conditions vary, so too tymitons are the same, but vary with local conditions. While there is no earthly equivalent to time in our universe, I will constantly be referring to the ocean, for no other analogy is closer.