The Moon held the oldest calendar in human civilization. Babylonian priests tracked its 29.5-day cycle to fix the months, predict eclipses, and time religious festivals. The lunar god Sin presided over Ur, one of the greatest cities of Mesopotamia. His crescent symbol appeared on boundary stones and royal seals. Egyptian religion gave the Moon to Thoth, god of writing, measurement, and the reckoning of time. Thoth's ibis head and lunar disk connected the Moon to record-keeping, magic, and the judgment of the dead.
Greek astrology split the Moon between Selene, who drove the silver chariot across the night sky, and Artemis, goddess of the hunt, wilderness, and childbirth. Ptolemy classified the Moon as cold and moist, governing the body's fluids, the brain, and the left eye. He placed it as ruler of Cancer and noted that the Moon's speed made it the fastest-changing influence in any birth chart. Medieval astrologers called the Moon the 'Lesser Luminary' and linked it to silver, pearls, and the tides.
Modern astrology transformed the Moon into a symbol of the inner self. Dane Rudhyar, writing in the 1930s, reframed the Moon as the psyche, the repository of childhood memory and emotional habit. In psychological astrology, the Moon sign reveals how a person processes feeling, what they need to feel safe, and how they experienced their mother or primary caretaker. The Moon moves through all twelve signs in roughly 28 days, making it the fastest-moving body in the chart and the most personal.