How does this compare to confirming the existence of other things demonstrated to exist? For example, do we confirm the existence of a proton as some percent of

How does this compare to confirming the existence of other things demonstrated to exist? For example, do we confirm the existence of a proton as some percent of the universe of protons? The same for gravity? Magnetism? Why is it that with time, we are always using some kind of tolerance statement based on some understanding of the entire existence of the universe (which I am unclear on how to test such theories), meaning that we still are not coming to a single statement "time is x" while also assuming time to exist (I haven't seen things published such as "we are less than 1/10th of a nuclear force inaccurate" because this is not how the nuclear force is demonstrated to exist)? To me, this suggests there may be certain broadly predictable properties of the universe such that time seems to explain some aspect what we observe, but it is merely concurrent with the mechanics of the universe and useful for human understanding, but not something that exists (note that this is my interpretation, not a scientific proposition). (Conceptually similar to how the Ptolemaic model of the universe can predict the cycles of the stars, but does not provide a description of how the universe works, but I'm not trying to change the topic, just to stick strictly here to demonstrate things can be useful and scientifically not true.)