Was one of the early Egyptian calendars a 365-day calendar?
Yes. The earliest Egyptian calendar was based on the Moon’s cycles, but later the Egyptians realized that the “Dog Star” in Canis Major (which today’s astronomers call Sirius), rose next to the Sun every 365 days, about when the annual inundation of the Nile began. Based on this knowledge, they devised a 365-day calendar that seems to have begun around 3100 B.C.E., which thus seems to be one of the earliest years recorded in history. Before 2000 B.C.E., the Babylonians (in today’s Iraq) used a year of 12 alternating 29-day and 30-day lunar months, giving a 354-day year. In contrast, the Mayans of Central America relied not only on the Sun and Moon, but also the planet Venus, to establish 260-day and 365-day calendars. This culture and its related predecessors spread across Central America between 2600 B.C.E. and 1500 C.E., reaching their apex between 250 and 900 C.E. They left celestial-cycle records indicating their belief that the creation of the world occurred in 3114 B.C.E. Their calendars later became portions of the great Aztec calendar stones.