What would be the right way of starting (and developing) a discussion on the subject "What is time?"? Most probably in a number of ways as (paraphrasing Aristotle, 1003a) time has many meanings. Perhaps it would be sensible then not to start at all, think it over once again and limit the theme in an appropriate way. In the following we ask what time is, and follow namely this appeal — we think again and restrict the subject.