The Lunar Calendar and the Myth of the 13th Sign
This tool allows you to visualize the true rhythm of lunations and understand the astronomical origin of a famous enigma: the myth of the 13th zodiac sign.
Tropical Astrology: A Solar Science
To understand the value of this calendar, a fundamental point must be recalled: tropical astrology, the basis of Olwhyde, is a solar science. The zodiac is not based on visible constellations, but on the division of the Sun's annual path as seen from Earth into twelve equal sectors. The beginning of Aries corresponds to the spring equinox, a precise solar point. Mastering this zodiac has always required advanced astronomical calculations to track the Sun's position.
However, many ancient cultures, lacking these calculation tools, relied on a simpler cycle to observe: that of the Moon. It was easier to count New Moons than to calculate the exact position of the Sun. This practical approach led to the development of lunar or lunisolar calendars (like the Hebrew calendar) and, by extension, to historical confusion.
The Origin of the Myth: 12 Solar Months, but Sometimes 13 Moons
The heart of the problem comes from a simple mathematical discrepancy: a solar year lasts about 365 days, while 12 lunar cycles (lunations) last about 354 days. Each year, there is therefore a gap of 11 days. For a lunar calendar to remain aligned with the seasons (which are solar), it is necessary to periodically add a 13th lunation.
This astronomical reality is the true source of the "13th sign" myth. The idea that a sign was "forgotten" comes from this periodic 13th moon. Some have wanted to associate this 13th sign with the constellation of Ophiuchus, which is a double error:
- Tropical astrology uses the zodiac of signs (12 x 30°), which is a mathematical division, not the zodiac of constellations, whose sizes are unequal.
- The 13th cycle is not a sign but a lunation, a cycle of the Moon and not the Sun.
What This Calendar Shows You
This lunar calendar is an observational tool. It is not designed for tropical astrological interpretation, but to visualize the real rhythm of the Moon and understand celestial mechanics. It allows you to see concretely:
- The years that have 12 lunations and those that have 13.
- The exact date of each New Moon that begins a lunation.
- How the lunar cycle shifts in relation to the solar year.
By observing this phenomenon, the confusion between the lunar cycle and the solar zodiacal cycle disappears, and the myth of the 13th sign finds a simple and logical explanation.