Ancient Date Notation Systems
Other researches describe proofs of the fact that the minds and actions of the earthlings are affected by calendar processes, yet it is commonly considered that some events are destined to take place regardless of time spans. Nothing can be dramatically changed by solely calendar periods.
Archaic scientists (stargazers, priests of diverse spiritual disciplines) were very close to rulers of their countries. Their works were stored in guarded libraries and so many of astronomic as well as related knowledge were kept safe. Coverage of that ancient knowledge soon became sufficient for development of precise time-measurement systems.
According to pieces of knowledge found in ancient manuscripts, we can conclude that namely Sumerians were the leading civilization to design a Sun-driven calendar (~2000 B.C., Mesopotamia), which contained 365 days. Also we can well note Babylonians (~2500 B.C.) who developed a calendar based on the Sun’s and the Moon’s periods. In its turn, Babylonian calendar made a foundation for the Hebrew one which appeared later.
Among other ancient cultures, the Chinese are respected creators of the most precise (by that epoch) Moon calendar (~450 B.C.) Regardless of being aligned on Moon’s cycles, actually it was not far from calendars of Babylonians and Hebrew; it incorporated 365-day year as well and the opening date of different years didn’t coincide.
From relatively modern civilizations, it is the Mayans who came up with remarkably precise calendar on their own (~ 9–10th century A.D.). The time difference between their calendar and the Gregorian (modern) one doesn’t exceed 60 seconds per year.
Omar Khayyam, well-known poet and astronomer of Middle Ages, contributed a time system which is now called the Persian calendar. It outperformed Mayan calendar in terms of accuracy. The Persian calendar proved to be even more precise than the Julian calendar (predecessor of Gregorian), which empowered its adoption in different cultures of Middle Ages. Remarkable fact is that Omar Khayyam derived almost ideally precise duration of the Sun’s year equal to 365.24219858156 days (which is absolutely accurate up to the 6th decimal place according to modern astronomy).