4. Lunar Mansions

The Lunar Mansions sacred calendar is actually pretty simple to comprehend. The basic idea is that ancient astrologers divided the sky into 28 major sections (“mansions” [see Fig. 1]), each about 13º wide when seen from the earth—roughly the width of a human palm when outstretched from the body. Within each of these mansions, a major or governing star was identified that lent its name and meaning to that mansion (see Fig. 1 above).

As the moon orbits around the earth, it passes through these 28 mansions in order one at a time. Given that the moon completes its orbit in roughly 27 days (the sidereal period, or time relative to the stars, is 27.321661 days [see Fig. 2]), this means that the moon passes through almost exactly one mansion per day.

Thus each day on this calendar can be identified by one of 28 unique names (to keep the calendar on track, one mansion is skipped roughly every ≈38 days).

Not only this, but as the moon orbits the earth its phase as seen from the earth also changes. This means that beyond the 28 unique names given to each day there are also eight major phases that the moon passes through in roughly 30 days (the synodic period, or time relative to the sun—from new moon to new moon—is 29.530588 days [see Fig. 3]).

This offset, between the synodic period and the sidereal period, means that the moon does not return to the same phase and mansion but once every ≈355 days, which is to be expected given that the scientific length of a lunar year is 354.37 days.

As described above, the Lunar Mansion calendar is computed based on the position of the moon relative to the stars (sidereal, or which mansion it is in) and the sun (synodic, or what phase the moon is in).

This means that each month the moon will pass through all the mansions and all the phases in slightly varying combinations. We can illustrate this with a visual example.

Fig. 4 shows the moon aligned to the mansion of Sadachbia or Gamma Aquarius (for reference, this mansion is called “Body” in the sacred calendar). Due to the position of the earth in its orbit around the sun, this alignment occurs during the moon’s new phase when it is so near the sun that it cannot be seen (unless there’s an eclipse). Since we know what stars are behind the sun at any given time of the year, it is entirely possible to know what mansion the moon is in despite not being able to see the moon during this day. (For reference, in the sacred calendar this phase of the moon is called “Hid” in the case of this positive mansion.)

Fig. 5, however, shows the exact same alignment of the moon to Sadachbia or Gamma Aquarius but half a year later when that star is visible at night. In this case, the moon’s phase when aligned is the full phase (in the sacred calendar this is called “Comprehended” in the case of this mansion). This is because the moon is fully behind the earth compared to the sun and now its face is fully illuminated when passing through this mansion.

In the case of Fig. 4, the sacred day would be called “Hid Body” and carry certain significance associated with that unique combination. Half a year later, the sacred day associated with this mansion has changed due to the differing moon phase, and the sacred day associated with this alignment would be called “Comprehended Body,” which would carry with it an entirely different meaning.