One group insisted that we should simply accept 2001 as the start of the Millennium. In anycase, they continued, one always starts abstract things like time or distance from zero. It is our understanding of the concepts of zero, of mental-scale demarcations and of counting and naming virtual objects, which are mixed up. As such, it initiates the count by helping our perception but is not part of the count itself. This is because named intervals are more concrete than the scale itself.
Nobody tries to conceptualize the magnitude and meaning of an infinitesimal point of time.
It is normally marked for us externally by a clock scale. Therefore, intervals are almost like concrete things that we name and refer to. Before the clock strikes one, we do not have an hour yet, neither do we call it hour zero. We have a fraction of an hour in minutes and seconds. When the first hour has passed, we now have a count and a reading.