The reckoning of time helps people to better understand the passage of time. However, people used to write down time differently than they do today. So anyone interested in the history of ancient peoples sometimes has to learn a different way of reckoning time.
Time reckoning means dividing up the year. It also means counting the years one after the other so that you know how long ago an event happened. Nowadays, for example, we say that the Berlin Wall fell in 1989. So there must be a zero point, a starting point from which you count the years until 1989.