Months used to be based on the moon in ancient cultures.
Even a simple consideration of our English word "month" shows a clear etymological connection to the word "moon."
The ancient Latin word signifying a month was "mensis," which survives today in its plural form to signify a woman's monthly cycle, which is also correlated with the cycle of the moon and the two cycles have traditionally been associated (although this has in recent years been hotly contested by "modern science" which wishes to declare that there is no correlation: see a few sample articles and medical studies on the debate here and here).
Scholars believe that the ancient Romans followed a lunisolar calendrical system, in common with many other ancient cultures. Indeed, our very word "calendar" comes from the names used in that ancient Roman system (we will return to that point in a moment).
In a strictly lunar system, months will be measured by observation of the moon, with the new month typically commencing at the first observation of the brand new sliver following the New Moon. Because the periods of the moon's cycle do not subdivide the solar year evenly, a strictly lunar system is not well suited for also observing the renewal of the solar cycle (the year, as opposed to the month).
If the moon-driven months do not go evenly into the sun-driven year, then a strictly lunar calendar system will have no way of preventing the start of a year from drifting into different seasons (winter, spring, summer and fall being functions of earth's relationship to the sun). Therefore, ancient cultures followed lunisolar systems which followed the moon for the months, but added modifications in order to keep the observation of new year tied to the sun's cycle as well, typically observing the "renewal" of the sun at either the winter solstice or the spring equinox.
One common mechanism for making a lunisolar calendar involved measuring the months based on the cycles of the moon, and measuring the year by a certain number of lunar months, but then inserting an extra month (known as an "intercalary month") into the year periodically, in order to make up for the discrepancy caused by the fact that the solar year does not divide evenly into lunar months. The ancient Hebrew system for doing this (a system still preserved to this day) which was related to systems in use in ancient Mesopotamia, is described in the video below showing part of a lecture by the late Professor David Neiman (1921 - 2004):
As Dr. Neiman explains in that video, twelve lunar months alternating 29 days and 30 days apiece (because the actual cycle of the moon does not exactly divide into terrestrial days either, but is longer than 29 and shorter than 30) adds up to 354 days (you can easily confirm this using your phone's calculator, if you desire, by adding 29 and 30 for a total of twelve times, or six pairs of 29 and 30, which sums to 354).
Thus, the first day of a year composed of twelve lunar months will obviously drift rather rapidly away from the same time of the year from one year to the next (if you begin the count of months for one year in winter, for example, you will soon find that the start of the year is taking place in the fall, if you keep starting a new year only 354 days after the previous year -- and not long after that the new year will begin in the summer and then in the spring).
To keep this kind of drift from getting too large, and to bring the calendar year of lunar months back into synch with the solar cycle which governs the seasons, one method used by ancient traditional lunisolar calendars involved adding an additional lunar month to the year periodically, so that some years would have 13 lunar months before celebrating a new year.
As the video above explains, the ancient Hebrew lunisolar system (which is related to ancient Babylonian lunisolar systems) would add this 13th lunar month after two years, because a 354-day year (based on 12 lunar months) would be eleven days short, and so adding a 13th ("intercalary") month of 30 days after two years (when the calendrical year had fallen behind by 22 days) would bring the new year back to within three days of the actual solar cycles that started two years before (because in that third year, without the intercalary month, you would then be behind by 33 days, but adding in an additional lunar month of 30 days would bring you to within three days of the three solar cycles that had been going on all this time that you were measuring months by the moon).
Thus, after three years of lunar months (with 12 lunar months in the first two years and a third year with 13 lunar months), your calendar would be about three days behind (the extra month of 30 days almost, but not quite, catching up to the 33 days that the lunar system fell behind the solar cycle).
Following this pattern again for the next three months would mean that the calendar of lunar months (12, 12, and 13) would be behind by six days (three from the first three years, and three more days behind after the next three).
After six years of lunar months (12, 12, 13, 12, 12 and 13) and six days of displacement from the solar cycle, the next (seventh) year of twelve lunar months would add another 11 days of displacement from the solar cycle, for a total of 17, and without an intercalary the next (eighth) year of 354 days would bring the total to 28.
But, as Professor Neiman explains in the lecture above, adding an intercalary lunar month of thirty days in the eighth year brings the lunisolar calendar into very close alignment with the solar cycles, because of course the solar cycle does not divide evenly into earth days either -- it is not exactly 365 days long but rather a number closer to 365.2422, which we know about because our solar-based calendar system inserts an extra day into "leap years," which happen every four years (except on years ending in 00 which are not evenly divisible by 400, such that 2000 was a leap year since it is evenly divisible by 400, but 1900 was not a leap year since it is not evenly divisible by 400, this rule being instituted because a year is not exactly 365.25 days long either, so having a leap year every four years would be too much).
Thus, the fact that the solar cycle repeats every 365.2422 days (almost 365.25 days) means that after eight such cycles, the "day count" must be increased by almost exactly two full days (which could be accomplished using the leap year system with which we are familiar, for example). That's why the lunisolar system described above, which adds another intercalary month in the eighth year, will bring the lunisolar calendar back into near-perfect agreement with the solar cycle (12 lunar months, then 12, then 13, 12, 12, 13, 12, 13) -- because the lunar counts fall behind by 28 days and add 30 days with the intercalary month in the eighth year, and someone keeping an accurate solar day-count over the same period would have to add two days somewhere in those same eight years, bringing the two systems into alignment.
The ancient Norse and Germanic cultures used a lunisolar system, as did the ancient Celts, the ancient cultures of India, the ancient cultures of Mesopotamia, and those of ancient China and Japan, and many others as well. The traditional observation of lunar New Year in China and surrounding nations also follows the ancient lunisolar systems preserved in those East Asian cultures. The cultures of ancient Greece also employed lunisolar systems, each with slight variations but all intended to accomplish the same goals described in the foregoing paragraphs. And, as mentioned above, the ancient Romans also appear to have followed a lunisolar system -- but they began to modify the system in rather unusual ways and finally jettisoned the lunisolar approach altogether during the time of Julius Caesar.
The vestiges of the ancient Roman lunisolar system can be found in special terms which were applied to certain days each month, and which continued to be used after the older system was altered (and are still used, somewhat poetically, in modern English). These terms seem to preserve the original strictly lunar character of the months. The Romans called the first days of each month were called the "kalendae" (the Latin plural is usually changed to "kalends" when translating this word into English). One week later came the "nonae" (which in modern English has been changed to the "nones"), and two weeks after the kalendae came the "ides" (which is the most familiar of these three special day-designations to us in modern times), on the 15th of the month.
Scholars believe that these vestigial terms, still in use in the classical Roman era, must reflect an earlier system in which each month began at New Moon (the day of the kalends). In such a system, the day of the nones would mark the arrival of the First Quarter, and the ides would of course mark the arrival of the Full Moon.
We still talk about the "ides" even to this day, in conjunction with the 15th of the month (most commonly in the United States when referring to the "ides of April," on which income taxes are typically due to be paid, and of course the "ides of March," on which day Julius Caesar was assassinated).
However, we now use a calendar system in which the months are completely divorced from the cycle of the moon, such that the term "ides" designates the 15th day of a month that does not synch with the moon and which thus has no connection to the Full Moon whatsoever.
It is in fact ironic that we call our calendar system by a name derived from the word "kalends," which was the name for the first day of each month -- the day which would be indicated by observation of the first thin sliver-crescent of the New Moon. Our calendar system requires no observation of the cycles of the moon at all, and by its very arrangement seems to imply that the moon is irrelevant to our daily lives -- when of course the moon is not irrelevant at all, but is intimately connected to the very cycles by which new life is conceived and the family of humanity is preserved.
It is ironic that the date of Easter, out of all the holy days observed by the Christian faith, relies upon a lunisolar calculation, involving the arrival of the Full Moon following the March equinox (the rules for its calculation are rather complicated and involve calendrical tables which do not always correspond with what one would expect based on the actual lunar and solar activity which can be observed in the sky itself).
The lunisolar character of Easter is ironic because literalist Christianity can be shown to be aggressively solar in almost every way, from its designation of Sunday as the day of worship, to the solar alignment of its churches, to its preservation of four canonical gospels one of which is longer than the others, one of which is shorter than the others, and two of which are about equal length of a length that is in between the longest and the shortest, just like the solstices and the equinoxes (and which are traditionally associated with the figures of the Lion, the Ox, the Eagle, and the Man, which correspond to constellations marking the solstices and the equinoxes in the precessional Age of Taurus, as discussed in this previous post).
It is also almost certain beyond any doubt that the triumph of literalist Christianity was accomplished in conjunction with an underground secret society known as the cult of Sol Invictus, whose name means "the Unconquered Sun" (or the "Unconquerable Sun"). And it is of course notable that literalist Christianity soon set about imposing a strictly solar calendar upon the world wherever it went.
Thus, it is ironic that the date of Easter maintains a distinctly lunisolar aspect, despite ongoing calls to fix it to a date that will not wander so much, such as "the second Sunday in April each year," a proposal which would strip it of any lunar elements and attach it to the day of the sun in a month whose starting and ending (as with all the other months) no longer has anything to do with the cycle of the moon.
Thus far, however, the date of Easter remains tied to the cycles of the moon in relationship to the solar cycle landmark of the March equinox.
We obviously owe this ongoing lunisolar observation for the date of Easter to the fact that Easter is connected with the observation of the Passover (the Last Supper in the Passion Week being described in the gospel accounts as an observation of the Passover meal), and the observation of Passover is of course tied to the ancient lunisolar systems described above.
We might say that the lunisolar nature of Easter is a last grudging concession within literalist Christianity to the ancient lunisolar systems which were once observed by the nations of the world (whose traditions the literalists soon set out to destroy wherever they could).
Lunisolar traditions also survive in the observation of Lunar New Year as mentioned above, as well as in many sacred days and festivals within Hinduism and Buddhism and others to this day.
The complete disconnection of most men and women from any awareness of the cycle of the moon in modern western cultures (upon whom the strictly solar calendar was imposed centuries ago) must undoubtedly be reckoned a terrible catastrophe. The motions of the moon appear to have measurable effects on our bodies and internal cycles, and they clearly have an impact upon the seas and mighty oceans, and upon the daily tides.
As mentioned in my previous discussion of the Tychos model for explaining the observed motions of our solar system (see here), Tychos discoverer Simon Shack has found evidence which strongly suggests that our moon itself is not just some "random appendage" whose orbit around earth has nothing much to do with the rest of the solar system, but rather that our moon itself and its orbital cycle has undeniable harmonic resonance with the orbital cycles of Mercury, Venus, Mars, Jupiter, Saturn, and even the outer planets as far as Pluto!
Based upon his findings, Simon proposes that our moon may in fact function as "some sort of 'central driveshaft' for our entire system," meaning for the entire solar system.
If so, it would certainly seem wise for us to pay much more attention to the cycles of the moon than we do today -- and the evidence overwhelmingly demonstrates that the ancients did indeed pay much more attention to those cycles, prior to the replacement of the ancient lunisolar calendars and the aggressive enforcement of a strictly solar system which removed the role of the moon altogether.
However, here in the Holy Week in between the observation of Palm Sunday (this past Sunday, which was a Full Moon) and Easter, we have a clear reminder of those more ancient systems which once were observed the world over.
The very fact that Easter's date is celebrated at very different times each year, based upon the cycles of both the moon and the sun, should hint to us that these ancient stories are in fact metaphorical in nature, and that they have their basis in the celestial motions in the heavens above, rather than in literal and historical events. You can find my extensive discussion of the celestial foundations of a great many of the Easter Week events described in the gospel accounts in my 2016 book Star Myths of the World, Volume Three: Star Myths of the Bible (along with numerous illustrations and star-charts).
Some of those events which are explored and whose celestial foundations are explained include:
- The triumphal entry into Jerusalem
- The cleansing or scourging of the Temple
- The cursing of the fig tree
- The Upper Room and the Last Supper (including the Foot Washing episode)
- The Garden of Gethsemane, and of course
- The Crucifixion
