 Time is intimately related to the cycles in the sky, let alone the day-night alternation that we mentioned. That's, of course, the most basic unit of time. But to go beyond that, to go beyond the simple observing that there is a period of light and a period of darkness that repeats every 24 hours, really the moon was central. The phases of the moon and the lunar cycle of 29.5 days was absolutely crucial in enabling the understanding that we can measure time spans that are longer than a day