13 Month Lunar Calendar — 13 Phases Of The Moon

Time for a 13 Month Lunar Calendar — 13 Phases Of The Moon

In times past, many cultures use a 13 month lunar calendar, rather than the twelve months.  Perhaps it’s time for the world to consider a calendar based on our closest celestial satellite rather than one based on the mythology of the Zodiac?   Learn why it makes sense.

The Moon is our closest celestial partner. But our calendar uses star constellations of the Zodiac. Before we get to why we use the Gregorian calendar, let’s look where the 13 month lunar calendar originated, and see why returning to a calendar based on 13 phases of the moon makes sense.

Depending on how you measure them, the moon circles the Earth 13 times in a yearly cycle.  Each cycle of moon phases takes 28 days to complete.  Here’s the issue with any calendar, it must account for the fact that the solar year is 365.25 days.  So, for your calendar to coincide with the specific solar festivals, you must account for an extra quarter of day.  Today, we have a leap year every four years, when the month of February has 29 instead of 28 days.

The 13 Phases of the Moon

Our lunar partner changes from day to day during the 28 days in each cycle, so you would need a telescope to see the difference.  However, there are ten distinct cycles that are easy to recognize without the need of magnification. Almost every ancient civilization used lunar cycles as the basis for their calendars.  Ethiopia uses a 13 month lunar calendar today.

People could see how the moon affects daily life.  They can see the correlation between the lunar cycles and the ocean’s tides. And, since we are mostly water, it is possible to feel the effects.  Some plants and animals respond to both a circadian rhythm and a lunar clock. They can use the cycles of moon to calculate migration of animals, birds and insects.  Think of each of these 13 moon phases like a snapshot.

There is anecdotal evidence that crime rates rise when there is a full moon. It’s where we get the term lunacy. See also Old French lunatique, from late Latin lunaticus, and Latin luna moon. The term lunatic derives from lunaticus, which initially referred to epilepsy and madness. They believed that our lunar satellite could cause these and other mental disorders, including intermittent insanity.

Do you relate to one cycle more than the other? Do you notice your mood change with these cycles? It draws many people to a specific lunar phase. Indigenous cultures used the bright lunar reflection for hunting and fishing. It also signaled critical times for planting and harvesting. Are the 13 phases of the moon a part of our DNA?

The Cycle of the 10 Main Moon Phases

13 Moon Phases And The 13-Month Moon Calendar

One way to measure these cycles is to divide them into ten easily recognizable portions. Our lunar partner has 5 waxing phases (1).

Waxing means getting larger. We see more of it as it moves from a New to a Full Moon. Then there are five more waning phases. Waining means getting smaller. So, the satellite’s visible portion gets smaller from the Full Moon to an Old Moon.

Waxing Lunar Cycles

1) New

The new moon happens when the moon is directly between the Earth and the Sun, so you can’t see the moon.  A solar eclipse can only happen at the new Moon.  Of the 13 moon phases, this one is easy to miscalculate because of cloud cover.

2) Young

A young moon is a crescent New Moon crescent that is less than 30 hours old. Or 30 hours from the beginning of the new Moon.  You need to plan in order to see this phase. And, this short-lived phase is usually only viewed in the west.

3) Waxing Crescent

A waxing crescent is when it looks like a crescent, and the crescent increases (waxes) in size from one day to the next.

4) First Quarter

The first quarter lunar cycle (or a half-moon) is when half of the lit portion is visible after the waxing crescent phase. It comes a week after a new moon.

5) Waxing Gibbous

This cycle occurs when we can see more than half of the lunar sphere. The visible portion increases (waxes) in size from one day to the next. The waxing gibbous phase occurs between the first quarter and the full Moon.

Waning Lunar Cycles

6) The Full Moon

These moon phases occur when we can see the entire lunar sphere. This phase occurs when it is on the opposite side of the Sun, called opposition. A lunar eclipse can only happen at the full Moon.

7) Waning Gibbous

A waning gibbous moon occurs when we can see more than half of the lit portion, and the size decreases (wanes) in size from one day to the next. The waning gibbous phase occurs between the Full Moon and third quarter phases.

8) Waning Quarter

The last quarter cycle (or a half-moon) is when half of the lit portion is visible after the waning gibbous phase. A waning crescent is when the Moon looks like the crescent, and the crescent decreases (wanes) in size from one day to the next.

9) Last Quarter

The last quarter cycle (or a half-moon) is when half of the lit portion is visible after the waning gibbous phase. A waning crescent is when the crescent decreases (wanes) in size from one day to the next.

10) Old

An Old Moon occurs when you can see only a tiny portion of the lunar surface’s reflection. It is about to turn into a new moon.

Contemplating the 13 Month Lunar Calendar

13-month calendar

Now let’s examine whether it is time to contemplate a different way to measure the calendar year. It isn’t a new idea. In 1582, the Church and, therefore, the civilized world began using the Gregorian Calendar.  Its use was not out of convenience.  Using this calendar was a way for the Church to exert its power.

Before that time, a calendar of thirteen months based on the cycles or phases of the moon was the standard way to measure the year.  The Egyptians, Druids, Incas, and Polynesians have calendars based on our lunar partner cycles—even the Mayans with the most complex and correct Calendar in history used a calendar based on the 13 phases of the moon.

It is also evident that these cultures watched the sky intently. They celebrated the cycles of the Sun. The Sun, Moon, and Stars’ movements are part of the culture that became inscribed in many sacred texts. Some of these ancient cultures could recognize the planets, even though they did not have telescopes.

The celestial bodies’ activities are fundamental themes in many superstitions and religions. Their importance is evident in ancient architecture. The sun and moon cycles are significant themes in stone circles, wats, and sacred architecture of all kinds. Some structures have interior rooms that align with the Sun and Moon during specific celestial alignments. Stonehenge is an example of a building that aligns with mid-summer and sunrise and midwinter sunset.

As mentioned before, Pope Gregorius (Gregory Xiii) created the Calendar we use today. That’s where the Gregorian Calendar gets its name. The result is a chaotic calendar. It’s tough to follow and out of phase with our planet and the Moon. We have Months with 29, 30, and 31 days, and once every four years, February has 28 days! We need leap year (2) based on a complex formula. It’s a similar type of chaos we have with daylight savings time.

Julius Caesar’s astronomers created the 12-month year, one for each of the Roman leaders. Initially, each month had 31 days, but this made the year too long at 372 days. So, they shortened some months based on the importance of the leader. But, this is still inaccurate and requires the addition of a leap year to keep in sequence with the seasons.

The Roman Catholic Church gives us the Calendar with 12 months, not 13. It’s not accurate or practical, but it enforces its influence on the cultural narrative. Society conforms to its critical mass by adopting its values. There’s no rational reason to use this system of measure.

Math Simplicity

So, let’s do the simple math related to Earth’s annual cycles. Each lunar cycle has 28 days. And 28×13 = 364 days + 1 day out of time. This last day is a day of love and peace. It was a day of meditation and happiness before the new year.

Unlike the Gregorian Calendar, the days of each complete lunar cycle (month) and the days of the week line up perfectly. It makes the 13-month moon calendar or a 28-day calendar a perpetual calendar. A perpetual calendar means we fix every date to the same weekday every year. It makes it easy to plan way ahead and reestablishes our connection to the Universe.

Moses B. Cotsworth proposed a similar calendar based on the 13 phases of the moon in 1902. This solar Calendar also divides the year into 13 months of 28 days. But, it makes more sense than our current Gregorian Calendar.

Moon phases provide a simple and harmonious 13 month lunar calendar. With this system, the logic is simple to follow. Each week starts with Monday and ends with Sunday. The 1st day of every month will always be a Monday, and the 7th is on Sunday.  It would make planning simpler.  The international fixed calendar was highly favored by transportation and logistics companies in the 1890s.  The Eastman Kodak Company promoted this idea and used in internally in the 1920s, but there wasn’t enough momentum or funding by other companies to make it a reality.  (3)

Final Thoughts on a 13-Month Moon Calendar

This discussion on the 13 moon phases highlights how organized religion has shaped our cultural narrative.  This integration took place generations ago, so most people don’t see it.  Just as daylight savings time was a bad idea, so is the 12-month calendar based on the Zodiac.


(1) Lunar Phases: https://en.wikipedia.org/wiki/Lunar_phase

(2) Time and Date: https://www.timeanddate.com/date/leapyear.html

(3) The Death and Life of the 13-Month Calendar: https://www.bloomberg.com/news/articles/2014-12-11/the-death-and-life-of-the-13-month-calendar

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