Here's a simplified timeline:
* Ancient civilizations: Ancient cultures like the Egyptians and Babylonians observed the cycle of seasons and the movement of the stars. They developed calendars based on their observations, which were quite accurate. For example, the Egyptians developed a calendar with a year of 365 days.
* Early astronomers: Greek astronomers like Hipparchus (circa 190-120 BC) refined the concept of a year by making precise measurements of the stars and planets. They calculated the length of a year with greater accuracy.
* Modern astronomy: With the development of telescopes and other instruments, scientists could observe the Earth's orbit around the sun with even greater precision. We now know the Earth's year is approximately 365.2422 days long.
So, while there wasn't a specific "discovery" date, the understanding of the length of an Earth year has been refined and improved throughout history.
