The Moon takes about 27.3 days to complete one orbit around the Earth relative to the background stars. This is also approximately how long it takes to travel through the entire zodiac.

However, the cycle of the lunar phases lasts about 29.5 days.

The phases of the Moon are formed by the relationship between the Sun, the Earth, and the Moon. The Moon does not produce its own light: it reflects the light of the Sun. As it moves around the Earth, we see different portions of its illuminated surface from here.

At the New Moon, the Moon is approximately in the same direction as the Sun, and from Earth we mainly see its unilluminated side. At the Full Moon, the Moon is approximately in the opposite direction from the Sun, and we see almost all of its illuminated face. The waxing and waning phases appear between these two positions.

The reason why the phase cycle lasts 29.5 days rather than 27.3 is that the Earth is also moving around the Sun. When the Moon completes one orbit around the Earth and returns to the same point in the zodiac, the Earth has already moved forward in its orbit. The Moon needs to travel a little farther to form the same angle with the Sun again and repeat the same phase.

This is why there are two different cycles: the Moon’s journey through the zodiac, which lasts about 27.3 days, and the cycle from one New Moon to the next, which lasts about 29.5 days.

Symbolism: the zodiacal Moon remembers; the lunar phase updates. One preserves the continuity of the cycle, while the other shows that this continuity is never a perfect repetition. Each return takes place within a new relationship with the Sun.