Keeping Track Of Time

How did people in the past keep track of time? In fact, how do we do it now? Whenever I asked my old boss when something had happened, he invariably replied, "Ooh, a very long time ago!"

Here are two examples. It is alleged that:

Gratillonius' commission as a centurion ended automatically after twenty five years;

that period had terminated the previous year;
after that, he had no right to continue leading Roman soldiers;
therefore, he is a rebel and a bandit.

The accused's head reels. He tries to count:

one spring, Una told him she must marry another and he joined the army;
the following year, he was on joint manoeuvres with the Twentieth;
the year after that, the Visigoths crossed the Danuvius;
unless they did it the year after that again;
the years in Ys are tangled together...

A Tyrian, noticing how precise a time traveler was about dates, decided that it would be profitable to keep better track of past time so he marked special events each year, then kept the events in order. Thus, he is able to tell a Time Patrolman that a shipwreck happened in the year between a venture to the Red Cliff Shores and the year when he caught the Babylonian disease. (Time Patrol, p. 317)

Another Anderson time traveler, asking what year he is in, is told that it is the seventh year after the great salmon catch. Our historical framework is not that of our ancestors.