Final answer:
The ancient Egyptian calendar was based on 365 days, correlated with the star Sirius, and divided a day into 24 hours. The Solar calendar of Egypt was informed by their detailed astronomical observations, which advanced the understanding of timekeeping and influenced future calendar systems.
Step-by-step explanation:
By the third millennia BCE, Egyptian math and astronomy had created a calendar of 365 days. They devoted the extra 5 days of the year to feasts honoring their most important gods. It was based on the star Sirius, which they kept careful track of due to its yearly cycle correlating with the flooding of the Nile River. They also calculated a day divided into 24 hours. The Solar calendar was based on the observations of celestial bodies such as the Sun and stars, including the careful tracking of Sirius by Egyptian astronomers. This contrasts with a Lunar calendar, which is based on the phases of the Moon, and was used by many other ancient cultures including the Babylonians. As Egyptian astronomy was well-developed, they noted 'zenial days' when the Sun was directly overhead, and while they did not incorporate leap years, their 365-day calendar marked a significant advancement in timekeeping and influenced subsequent calendars, including the Julian calendar introduced by Julius Caesar.