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Calendar: from 360 to 365



Amenemhet I

When did human beings adopt a 365-day year? Why does a circle have 360 degrees in it? What does one question have to do with the other? The answer has to do with the Global Flood, and how that Flood forced a change in the calendar, long after it happened.

Calendar history

The English word calendar derives from the Roman Kalends, for the first day of any month. Obviously the only conventional history of calendars is p0st-Flood history. (History of calendars. (2014, July 1). In Wikipedia, The Free Encyclopedia. Retrieved 18:07 UTC, July 7, 2014, from A casual glance at calendar history from this source shows some interesting trends.

The various civilized powers developed three kinds of calendar:

  1. Lunar calendars. Sumer, Greece (Hellas), and Rome had such calendars. A typical year had twelve months of 29 or 30 days each, for a total of 354 days. To stay current with the seasons, whoever kept the calendar threw in an extra month before the beginning of the next year. In the ancient world, priests or kings kept the calendar. (In Rome the College of Pontifices, or Bridge-builders to the gods, kept the calendar. Highest of these was the Pontifex Maximus, who usually made all the decisions.)
  2. Solar calendars. Ancient Egypt seems to have been first to adopt a proper solar calendar. The first Pharaoh to adopt a solar calendar was probably Amenamhāt I. (See Lockyer J.N., The Dawn of Astronomy, M.I.T. Press, 1894; reprinted 1970.) Then in 48 BC, Julius Caesar came to Egypt, chasing after Pompey the Great. What he did when King Ptolemy XIII’s chamberlain handed him Pompey’s head in a jar, others have written about. The relevant history here is: Caesar consulted with Sosigenes, court astronomer to Cleopatra VII, about the course of the Sun, the regular flooding of the Nile, and the latitude line called a Tropic that passed through Egypt (specifically through Syene, or modern Aswan). With this knowledge, Caesar invented his all-solar Julian calendar. On his authority as Pontifex Maximus, he inserted 67 days after December of one final consular year (46 BC) before the inauguration of the new consuls (Kalends of January, 45 BC) and ordered that his country keep the new calendar from then on. (He little knew, though he might have guessed, he would die less than fifteen months later.) Caesar proposed adding an extra day every four years without fail; Pope Gregory IX would later revise that when he observed the Julian calendar had fallen ten days behind the seasons. Most of the world uses this Gregorian Calendar today.
  3. Luni-solar calendars. Months in such calendars begin and end, without fail, on the new moon. To stay current with the seasons, these calendars throw in an extra month, or lengthen the last month. The ancient Israelites seem to have lengthened their last month (Adar) by another lunar cycle if the barley was not yet ripe in Jerusalem by the new moon. (Jones F.N., The Chronology of the Old Testament) In 350 AD, the great Rabbi Hillel II invented a nineteen-cycle calendar that would prescribe exactly when to throw in the extra month (Adar Veith or “VeAdar”) and when to add a 30th day to the months Tishrei and Marcheshvan (the seventh and eighth months, counting from the Passover month). Remarkably, the Hillel calendar has stayed true to the seasons better than any other calendar now in use, including the Gregorian.

The Egyptian calendar, best of all

The Egyptian case is the most interesting. Lockyer (1894) gave the best treatment of it. The ancient Egyptians originally kept a 360-day calendar with 30-day months. (James Ussher, Archbishop of Armagh, made the same observation while preparing his Annals of the World.) But at some point in Egyptian history, the regular flooding of the Nile River obviously started happening later each year than last. The Egyptians solved this problem by adding extra days to the calendar between their months of Mesori (last) and Thoth (first). (Lockyer, op. cit., pp. 243-8)

But when did the Egyptians make this change? Lockyer quotes one of his authorities, named Krall, on this point:

The calendars of the Mastabas, complete as they are, do not mention the epagomenes, whereas inscriptions of the period of the Amenamhāts refer to them. [This means the extra days] were…introduced in the meantime, but probably nearer the upper than the lower limit.

(The word epagomenon or epagomene is a Greek-derived word, meaning “brought into,” for an intercalary day or other interval.)

So maybe Pharaoh Amenamhāt I first started adding the extra day. But why did Egyptian society wait so long? Not more than five hundred years before Amenamhāt (12th Dynasty), the records failed to mention any intercalary days. Lockyer wonders about that, too:

In Egypt, above all countries in the world, owing to the regularity of the inundation, the true length [of the year] was…easily determin[able] [as] soon as that regularity was recognized.

Or in layman’s terms: the Nile floods like clockwork at the same time every year, without fail. So of course the Egyptians would have known how long the solar year was, as soon as they realized how regular the Nile flood season was.

Lockyer had a problem. He assumed the solar day has never changed its length, except for intervals we measure in microseconds, and then only after a major earthquake. Everyone around him assumed the same thing. No one had reason to doubt that. So the authorities Lockyer consulted, all assumed the Egyptians adopted a lunar calendar and “brought the lunar month with them.” But neither Lockyer nor any of his authorities could figure out why the Egyptians did not figure this out until within centuries of the Exodus of the children of Israel out of Egypt.

But of course Lockyer never considered that a violent event, the only event worthy of the name cataclysm, shorted the day by more than twenty minutes.

The Global Flood and the Calendar

God is a God of order. In Genesis chapter 1 He proclaims His creation of the world “very good.” Actually, the Hebrew “mo’ed tov” means more than “very good.” It means absolutely excellent!

God is also a Stickler for detail. Everything in God’s creation is rich in detail. And any man building something by Divine commission, must pay almost Divine attention to detail.

So why shouldn’t we believe God, in making the sun and the moon, gave these two bodies an exacting, regular, and almost resonating cycle? Why shouldn’t we believe, in short, that before the Global Flood:

  1. The length of the year was exactly 360 days.
  2. The length of the synodic month, or lunar cycle, was exactly 30 days.
  3. The new year began on the fall equinox (in the northern hemisphere), and with a new moon, without fail.

So what happened? The year never changed its length. (Danny Faulkner was wrong to suggest anyone thought that.) Instead, as Walt Brown (In the Beginning: Compelling Evidence for Creation and the Flood) points out, a subcrustal ocean, thirty miles down, broke containment at what became the Mid-Oceanic Ridge system. This happened within a 200-year interval centered on 3290 BC. After it happened, the continents first drifted, then crashed to the subcrustal chamber floor, then sank. As they sank, the earth spun faster, to conserve angular momentum. So one day went from 1/360 year to 1/365.24 year.

At the same time as the breakout, as much as four percent of the earth’s mass, as water, rock and mud, escaped into space. This material went into orbit around the sun. But within weeks, months, years, or even centuries, some of this material fell onto the Moon. In particular, seven large and heavy objects fell to the Moon and caused rock to melt and flow like lava. This formed the Ocean of Storms and the Seas of Rains, Cold, Tranquillity, and Crises, and Humboldt’s Sea and the Moscow Sea, among other such smooth land areas.

These impactors struck mostly on one side. That side now faces the earth, from tidal lock. But the impacts also slowed the Moon down. This made it drop into a lower orbit, and one with a shorter period. That’s why the synodic month is now aboug 29.5 days. And these days are themselves shorter, by twenty minutes each, than a day before the Flood.

When did this happen? Insight from Project Apollo

This did not happen immediately. The two changes did not even happen concurrently. At least one creation scientist knew this thirty years ago. D. Russell Humphreys (Humphreys DL, “The Creation of Planetary Magnetic Fields,” CRSQ, 21(3), December 1984, retrieved from had available the strengths of the remanent magnetic fields from samples of basalt (Apollo 16, Descartes highlands) and brecchia (Apollo 15, crater Dune, Lunar Appenine chain). The magnetic dipole moments of the two samples were remarkably different: 6.3 x 10^21 J/T for the basalt and 1.1 x 10^20 J/T for the brecchia. In contrast, the magnetic dipole moment of the Moon is less than 1.3 x 10^15 J/T. The Magnetic dipole moment of the earth as of 1980 was (7.94 + 0.05) x 10^22 J/T. The magnetic field of the earth was likely much stronger after events associated with the Flood strengthened it. (See below.)

What can these numbers tell us? According to Brown, the earth’s magnetic field strengthened tremendously from the melting of the earth’s outer core, and the line-up of millions of magnetic dipoles as a result. Something similar might have happened within the objects that formed out of the ejecta from the Flood. The heavier the object, the more magnetic ore it might hold. Basalt had to form from one of the Seven Impactors, or an object not much more lightweight than these. Brecchia would form from a far more lightweight impactor.

These objects took time to form. Seven big rocks did not break off, fully formed, from the edges of the cracked earth’s crust, to fall onto the moon the same day they flew out into space. Instead, they formed by accretion, from material that first got far beyond the gravity of the earth or the moon. When they struck, they slowed and dropped the moon to its present orbit. Before they struck, the moon kept the same orbit as before.

In addition, several smaller rocks, no larger than 200 meters in diameter (the length of two World Cup soccer fields), broke off intact. Any one of these could have formed the Dune crater. Its magnetic field strength would have been much smaller; hence the lower remanent magnetism that still exceeds that of the moon.

How much time did the Seven Impactors take to form, coast, and strike? No one can know. But the material that made them must have come from earth. They would not have remanent magnetism so much stronger than the magnetic dipole moment of the Moon itself. Even the free boulders had magnetism stronger than that.


The day, and the synodic month, were both longer than they are today, before, during and after the Global Flood. But the Flood started a process that would shorten the day, and shorten the synodic month even further, over centuries after the Flood. The Egyptians were the best astronomers of their day. They wouldn’t make a mistake like that. They were slow to correct that mistake, but not that slow.

Amenamhāt I is a good candidate for the “Pharaoh who knew not Joseph” (Exodus 1:8). Which suggests the calendar was slowly changing itself from shortly after the Flood, through the viziership of Joseph (Imhotep) and to a century or so before the birth of Moses. The Israelites probably kept up with the calendar in the easiest way possible: by observing the phases of the moon and adjusting them by when the barley ripened. So they might have had a good calendar by the time Jacob entered Egypt.

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Terry A. Hurlbut has been a student of politics, philosophy, and science for more than 35 years. He is a graduate of Yale College and has served as a physician-level laboratory administrator in a 250-bed community hospital. He also is a serious student of the Bible, is conversant in its two primary original languages, and has followed the creation-science movement closely since 1993.

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Fergus Mason

“material that first got far beyond the gravity of the earth or the moon.”

Then how did it hit the moon? Makes no sense at all.

Fergus Mason

“The stuff came back and smacked the moon later.”

Orbital mechanics says no.

Fergus Mason

“Under no circumstances could any object fall into an orbit that would bring it back to the same neighborhood?”

Most stable orbits will do that. However the odds of a chunk of ejecta that’s travelled beyond the gravity of the Earth/moon system falling into an orbit that intersects with the moon’s are rather remote. Seven chunks? If you believe that, why aren’t you in Vegas getting rich?

Fergus Mason

“What do you think caused the meteoritic bombardment of the moon and so many other bodies in the solar system?”

Asteroids. We KNOW this, OK? Brown’s wild tales of all those craters being caused by bits of Earth are just not credible.

Fergus Mason

“You mean, conventional wisdom says”

No, I mean we KNOW. If I’d meant something else I’d have said something else.

“a bunch of asteroids, for the origins of which you cannot account”

Of course I can. They’re leftover debris from the protosolar disk, which never coalesced into a planet because of Jupiter’s gravitational influence.

“Of course you can’t account for Mercury and Venus not having moons while all the other planets have them.”

Mercury is too small and too close to the Sun’s gravity well to stand a high chance of capturing a moon. The same may well be true for Venus; any potential satellite approaching the planet is very likely to get hovered up by the Sun instead.

“If you really thought you could defend convention that easily, you would not have backed away from his debate challenge.”

I’m happy to debate Walt Brown any time, on condition that he either stops demanding irrelevant personal information such as my military record or gives me a signed assurance that such information will not be given to anyone else.



The Earth expels up to 4% of its mass (no mention made here of the effect on the Moon’s orbit of this mass loss, but it should jump to a higher orbit) and then at some later date seven impactors strike the Moon on the same hemisphere, slowing it and driving it into a still-higher orbit. Correct so far?

It would be interesting to see a back-of-the-envelope calculation showing the energy budget for such a series of events. I don’t suppose you or Dr. Brown have something like that available? Hope springs eternal. I suppose it would start with calculating the orbital energy and angular momentum of the Earth-Moon system with an Earth ~2% heavier and a 30-day Moon orbit. Then conserve that orbital energy but drop the Earth’s mass by ~2% and determine the new orbital period and orbital angular momentum (the angular momentum should stay the same, I believe). Then calculate the change in angular momentum between that orbit and the current orbit, to see how much net angular momentum your impactors had to transfer to the Moon. Given a range of reasonable velocities for the impactors (ie not significantly greater than the velocity at which they escaped Earth, perhaps), that would give you a sense of the total impactor mass required. Or, on the other hand, if you had a range of impactor masses that you thought were reasonable, it would tell you the velocities required. At any rate, by controlling one or the other factor you could determine just how much energy would have been dumped into the Moon by the impactors – what a coup if the amount of energy is just right to cause some local melting and lava flows instead of shattering or melting the Moon completely!

Oh, and an explanation of when the Moon became tidally locked in its current orientation would be nice as well. If the impactors have to strike the Moon off-axis to slow down or speed up its rotation as well as its orbital velocity, the calculations get more difficult and the energies required go up quite a bit.

Shall we wait for your response or get started on our own calculations? If you have some sense of the limiting parameters like size or speed of impactor or strike angle, perhaps you could share them?


Well, it’s a slow rainy day here, so here’s my first draft, warts and all. I haven’t particularly checked the math: I’m more interested in the principle of the thing, so feel free to point out any errors you see. No doubt there are some.

Starting conditions: duration of Earth year is the same, but the pre-Flood Earth rotation is slower such that there are 360 days in a year, and 12 lunar months of 30 days each. The Moon is in a circular orbit, naturally. A month is 2,629,744 of our seconds long. During the Flood, the Earth sheds 2% of its mass. For the purposes of the math, this happens instantly. The Moon’s orbit goes through subsequent changes due to the loss of Earth mass and inelastic collisions with impactors that strike square on the leading hemisphere at opportune times. I’ve modeled this with four impacts using Hohmann transfer orbits to minimize the energy budget. The Moon plowing through the jet of Earthstuff is beyond the scope of this exercise. I believe that any other combination of impacts would require a greater total delta v for the Moon – this is a minimum energy setup – but that may well be incorrect. The Moon today has a mass of 7.348e22 kg, and its orbit has a semimajor axis of 384,748 km. All of these calculations will be treating the mass of the Moon as negligible compared to that of the Earth, which I know is a simplification but cut me a little slack here; I’ll be abusing significant figures too.

So: a preflood Earth of mass 6.09e24 kg (presently only 5.972e24 kg) with a Moon in a circular orbit of p = 2,629,744 seconds, with G the standard value of 6.672e-11 Nm^2/kg^2

We know that for circular orbits, p^2 = 4π^2r^3/GM, so solving for r gives 4.146e8 m; comfortably greater than the current apogee of the Moon. At that orbital distance for a circular orbit it would have velocity v = sqrt(GM/r) of 990.5 m/s.

Again, initially, r = 4.146e8 m and v = 990.5 m/s.

Then the Flood drops the mass of Earth by 2%, so the GM factor goes from 4.068e14 to 3.986e14 m^3/s^2. The Moon, continuing along at 990.5 m/s, is now traveling too fast to maintain a circular orbit; but by how much? Well, for a circular orbit at 4.146e8 m given v = sqrt(GM/r) the ‘new’ circular orbit velocity is only 980.6 m/s. Thus the Moon climbs into a new, elliptical orbit, where v = 990.5 m/s at perigee distance r = 4.146e8 m. Given that v = sqrt[GM(2/r – 1/a)] for our known v,r, and GM we find that a, the semimajor axis of the new orbit, is 4.232e8 m. So the period of the new elliptical orbit, where p^2 = 4π^2a^3/GM, is 2.740e6 seconds, or 31.2 of their old-style days.

We need to get from that orbit, with semimajor axis of 4.232e8 m, perigee of 4.146e8 m and apogee 4.318e8 m, to our familiar orbit of semimajor axis = 384,748 km, perigee = 362,600 km, and apogee = 405,400 km by using inelastic collisions with impactors. As far as I know, Hohmann transfer orbits are the most efficient way to do this, and would require four delta-v events. The first circularizes the elliptical orbit, the second two transfer the Moon down to a lower circular orbit, and the last one slots the Moon into its present elliptical orbit.

The first step is easy to calculate; we already found that the orbital velocity for a circular orbit around the current Earth at a radius of 4.146e8 m is 980.6 m/s. The Moon at this point is traveling 990.5 m/s at that radius; so our first delta-v must be -9.9 m/s.

Next we want a Hohmann transfer ellipse to take us from the circular orbit at r = 4.146e8 m down to a circular orbit at 4.054e8 m (the current apogee distance of the Moon). This requires two delta-v events; one to enter the transfer orbit and a second to leave it. Details are available upon request (nice review of the math is at ) but, long story short, the two are both -5.4 m/s, for a total for this step of -10.8 m/s.

Lastly we need one more event to drop the Moon from a circular orbit at r = 4.054e8 m to an elliptical one with perigee at 3.626e8 m. This is the big one – it requires a -27.7 m/s change.

So the total delta v for the Moon from its post-Flood orbit to the current one is -47.7 m/s, if you spread it over four impacts. The details of these collisions really depend upon the masses and velocities of the impactors. We can put some reasonable limits on the velocities involved – nothing is likely to be traveling faster than 10% of c, for example, so relativistic effects can be ruled out. The masses of the impactors probably have some reasonable limits as well – like less than that of Ceres at 8.958e20 kg (the largest asteroid in the Solar System).

The problem here is that the less massive the impactors are, the greater their velocity must be in order to produce the delta-v required. With inelastic collisions, as impactor mass decreases and impactor velocity increases, impactor kinetic energy goes up as the square of velocity. As a result more and more kinetic energy is ‘wasted’ in heating the impacted object. The fraction of kinetic energy lost in the collision is equal to the mass of the target divided by the sum of the masses of target and impactor. For example, one could take the edge case where impactors were traveling at 0.1c; to drop the moon to its current orbit would then require a total of 1.17e17 kg of impactors (divided up), or about 530 Halley’s comets worth. The energy release would be stupendous, though: 5.23e31 J total, of which only 8.36e25 J go into decelerating the Moon (0.00015%) while the remaining 99.9998+% goes to blowing it to plasma at infinity. It’s more than five times the Suns’ total daily energy output, and 100 times the gravitational binding energy of the Moon (~1.24e29 J).

On the other extreme, four impacts with Ceres-size objects would be more efficient in terms of how much energy was wasted in heat and blast effects, since the impactors wouldn’t need to be going so fast. Even those, however, would be fantastically energetic events, with ~98% of the impact energy going into heating. Take an impact with Ceres that produces one of those small -5.4 m/s delta v events for the Moon: that inelastic collision could occur at a stately 443 m/s, but that’s 1/2mv^2 = 8.78e25 J of kinetic energy in the impactor. The total change in kinetic energy of the Moon is only 1.07e24 J, which is only 1.2% of that total. So that’s 8.67e25 J that goes into heat and light – that’s an amount of energy comparable to the total amount of energy that Earth receives from the Sun over ten years! And that’s only one of the smallest delta-v events required!

If you can find a more energy-efficient way to move the Moon from your pre-Flood proposed state to the current one, please share it with us. If you have some other idea as to the size or speed of impactors that slowed the Moon down, I’d like to hear that as well. Maybe the pre-Flood moon was only a fraction of its current size, for example, so it’s momentum was much less. Maybe the impacts were magically elastic somehow. Otherwise there don’t seem to be any set of circumstances that allow the Moon to be slowed down by impacts in the last 5000 years and survive in the manner we know it today.


As for debating Dr. Brown – I really don’t feel the need. His ideas have no traction even among creationist researchers. Thanks in no small part to his own efforts, as far as I know, he’s the only one who works on his model. His worldview won’t outlast him personally. You, Dr. Hurlbut, are the only person that I know of who promotes his work. When Dr. Brown is confronted with the physical impossibility of his various theories he just jumps effortlessly to different topics, never addressing the uncomfortable conflicts. It is my foolish hope that you, at least, will eventually recognize that pattern. My responses here are an attempt to get you to do so.


Time will tell, I suppose.

If you see where I borrowed or carried incorrectly, or misplaced a decimal point, please do point it out. I have, as you see, run the numbers. My rejection, or at least my conditional rejection, of this Moon orbit claim is _based_ on my having run the numbers – and put them up here for critique. Surely you can do the same. Or don’t you have any? If you think my numbers are based on faulty assumptions, then say where you think the error lies.

Fergus Mason

“Walt Brown refutes the failed-planet theory of asteroids to which you refer”

No. He doesn’t accept it. There’s a difference.


Well, I noticed a mistake in my long post above: in the last paragraph I used “it’s” when I should have used “its”. So that’s a spelling error on my part. Have you found any math errors?

Here’s a thought – there may be a low-energy transfer trajectory for the Moon that would send it to the neighborhood of one of Earth’s Lagrange points and from there back into its present orbit with a smaller total delta-v; maybe as much as 20-30% less. The math for one of those twisty tube trajectories is beyond me, and I’m not sure it would even work since the Moon’s mass is not negligible compared to that of the Earth. But perhaps it’s the sort of thing that Dr. Brown had in mind. Do you think that would solve the energy problems for you?

Fergus Mason

“Just as you don’t accept the Hydroplate Theory.”

There’s a slight difference. No qualified scientist supports the hydroplate story because the evidence is solidly against it.

“You don’t dare accept it”

I don’t base the explanations I accept on irrelevant concepts like “dare”. I don’t accept it because it’s demonstrably wrong; it’s that simple.


If you can’t demonstrate, or even just pass along without comprehension, the calculations that were used to show that the Moon’s rotation and orbit could have been changed by collisions with seven impactors (or with however many your prefer) in the last 4500 years from some numerologically sanctified state to the current degenerate one in such a way that it was not destroyed outright while leaving it resembling anything like the Moon we see today, then your argument rests entirely on Dr. Brown’s authority, doesn’t it? It is, essentially, ‘Walt Brown said it, I believe in Walt Brown, and that’s the end of it’, isn’t it? If you literally have no idea – not even a rough hypothesis – about how massive the impactors were or how fast they were traveling or from what angle they struck or how much energy was released or any of the rest of it, then why should we find you at all credible?

I predict two things: you will not ask Dr. Brown about the math, and he will not volunteer it to you – because there is none. You don’t need to see the math, because you believe in his authority, and he doesn’t need to do any, because why bother? You already believe him.


To the best of my knowledge, Terry has never done a “back of the envelope” calculation to check anything Dr. Brown says. Some time ago, I presented a “Fire and Brimstone” analysis if only a fraction of the mass Brown says was launched fell back to Earth. Terry was invited to check my calculations with a quick BOE.

I know of several Physics PhD’s who have looked at Brown’s Hydroplate model. Each of them has come to the same conclusion I did. Basically, his proposal, if true, would sterilize the planet. One of the more notable is creationist astronomer, Dr. Danny Faulkner here:

Oh yeah… I’m no longer interested in Brown’s debate offer. IMHO, his time would be much better spent responding to Faulkner. I understand CRSQ would be delighted to publish Brown’s response.

[…] July 7, the National Creationism Examiner discussed the history of the calendar. At issue: the ancient Egyptians, of all people, had the best natural […]

[…] Calendar: from 360 to 365 […]

[…] Today many have developed more scientific theories to describe how this happened, even claiming to rely on evidence seen in the exploration of space.3 […]


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