@antiquidons Hipparchos concluded that the star Spica, part of the constellation #Virgo, had moved 2° relative to the #AutumnalEquinox.
When he compared the time it took the Sun to return to an #equinox with the time it took the Sun to return to a fixed star, he found a slight discrepancy. The equinoxes were moving ("precessing") through the zodiac, and that the rate of precession was at least 1° in a century. In other words: a full cycle through the zodiac is completed every 36,000 years.
@antiquidons#Astronomy and calendars are the domain of #Hermes. His grandfather Atlas turns the heavenly constellations and his mother Maia is one of the starry Pleiades.
Atlas instructed him in astronomy and the Greek mythographer Euhemeros says that #Aphrodite first established the constellations and taught Hermes. The planet #Mercury is attributed to Hermes because he first established the months and perceived the courses of the constellations.