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I am interested to know if there is convincing "astronomical" evidence/data to pin down the exact day of the week for the total lunar eclipse of April 14, 32 CE. I am hoping that perhaps this particular lunar eclipse's relationship to other eclipses (or with some other known astronomical event) might be of help. (I am using Stellarium software).

Background - My interest arises from the coincidence of this particular lunar eclipse relative to the Hebrew calendar date of Nisan 14 (the fixed Hebrew date of Passover on the Hebrew calendar). However, after consulting two competing "Hebrew" calendars, there appears to be some discrepancy concerning the day of the week (which is not surprising considering the historical complexities of Julian/Gregorian/Hebrew calendar reconciliation. One calendar places April 14 on a Wednesday while the other calendar source places April 14 on a Monday. Lastly, the Stellarium software has the eclipse occurring on Julian day 1732850 - but I don't know what that means. Can any of you astronomy gurus help me figure this out?

I am adding the following information as an answer (of sorts). I found the first passage on the Wikipedia page for "Week". All of the information below is triply consistent with the NASA eclipse pages, the contemporary Julian calendar, and with Torahcalendar, so I suspect that April 14, 32 AD is most likely correct as a Monday -

Passage from Wikipedia - "The continuous seven-day cycle of the days of the week can be traced back to the reign of Augustus; the first identifiable date cited complete with day of the week is 6 February AD 60, identified as a "Sunday" (as viii idus Februarius dies solis "eighth day before the ides of February, day of the Sun") in a Pompeiian graffito. According to the (contemporary) Julian calendar, 6 February 60 was, however, a Wednesday. This is explained by the existence of two conventions of naming days of the weeks based on the planetary hours system: 6 February was a "Sunday" based on the sunset naming convention, and a "Wednesday" based on the sunrise naming convention.[36]"

Similarly, I found that the February 6 date mentioned above appears to be again off by two days (this time Wednesday to Friday) when I consulted the Hebcal reference calendar that I used.

Interestingly, I also found that the saros 61 Lunar eclipse of Passover 32 AD is part of a "Metonic eclipse series" (five related lunar eclipses - saros 41/51/61/71/and 81) - which occurred between 7 BC and 70 AD. This series of five Lunar eclipses each occurred on roughly the same date and are separated by exactly 6940 days between them (each span equaling one 19 year Metonic cycle) - four in total spanning one 76 year Callippic cycle. The dates (and corresponding days) are as follows on BOTH the "contemporary Julian Calendar" and the Torahcalendar Hebrew calendar - April 14, 7 BC (Tuesday), April 14, 13 AD (Friday), April 14, 32 AD (Monday), April 15, 51 AD (Thursday), and April 14, 70 AD (Saturday). EACH of these April 14 dates fall on the eve of Passover because the 19 year Metonic cycle itself defines the "Luni-solar" aspect of the Hebrew calendar. However, it seems that the final eclipse date in this series of eclipses is the beginning date that history records for the "siege of Jerusalem in 70 AD" as well. The Jerusalem siege apparently ended with a sixth penumbral lunar eclipse (saros 48 of the next semester series) on September 13, 70 AD which was followed by a seventh penumbral lunar eclipse (saros 86 - last of the prior semester series) that occurred on October 8, 70 AD. - very interesting supporting information indeed.

Supporting Links:

https://eclipse.gsfc.nasa.gov/5MCLEmap/-0099-0000/LE-0006-04-14N.gif https://eclipse.gsfc.nasa.gov/5MCLEmap/0001-0100/LE0013-04-14P.gif https://eclipse.gsfc.nasa.gov/5MCLEmap/0001-0100/LE0032-04-14T.gif https://eclipse.gsfc.nasa.gov/5MCLEmap/0001-0100/LE0051-04-15P.gif https://eclipse.gsfc.nasa.gov/5MCLEmap/0001-0100/LE0070-04-14N.gif https://en.wikipedia.org/wiki/Eclipse_cycle https://en.wikipedia.org/wiki/Metonic_cycle https://en.wikipedia.org/wiki/Siege_of_Jerusalem_(70_CE) https://en.wikipedia.org/wiki/Week#Ancient_Near_East

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  • $\begingroup$ What do you mean by astronomical data? We can model the orbits of the Earth and moon and find that there was an eclipse 726598 days ago. That's April 14th (Julian) and you can look up the day. Days of the week are counted, not measured. $\endgroup$
    – James K
    Aug 22 at 0:37
  • $\begingroup$ By the way, any lunar eclipse in Nisan will aways be on Nisan 14, because the Jewish calendar is lunisolar, so the Nisan starts on a new moon, Full moon is always on the 14th. And lunar eclipses only happen on a full moon $\endgroup$
    – James K
    Aug 22 at 0:40
  • $\begingroup$ The next comment contains a live Python script that gives the day of the week for any Julian Day Number (by default, the JDN of the current date). If the day falls in the range AD 1-9999 it also shows the Gregorian date. Bear in mind that Julian days start at noon, UTC. $\endgroup$
    – PM 2Ring
    Aug 22 at 8:36
  • $\begingroup$ JDN to Day $\endgroup$
    – PM 2Ring
    Aug 22 at 8:37
  • $\begingroup$ Thanks @PM 2Ring (and @James) - Yes, I know that Passover is always "close to" the full moon (hence the eclipse coincidence), but I still question that it was on Monday "APRIL 12", even though that would strengthen the 14th (and the eclipse as per NASA) occurring on a Wednesday (see Hebcal.com). However, the other calendar source (Torahcalendar.com) seems to be more comprehensive, gives the specific Julian date, and definitely suggests otherwise. Here is the Torahcalendar link - torahcalendar.com $\endgroup$
    – user22542
    Aug 22 at 10:48
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The eclipse took place on the 14th of April in the Julian Calendar. The 14th of April 32AD in the Julian Calendar was a Monday. 32 was a leap year starting on Tuesday.

The confusion may be because the Gregorian calendar would have been two days behind the Julian, so in the Gregorian calendar, the eclipse is on the 12 of April (still on Monday)

Julian day numbers are an attempt to simplify dates and times. It is the number of days since noon (UT) on Monday, January 1, 4713 BC, in the Julian calendar. It avoids any worries about leap years or months and the time and date is just a number, so it is very convenient for calculations, but it isn't very human friendly.

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  • $\begingroup$ Thanks James. Yes, but that is the same information that I already had. Monday looks like it is the most likely day of the week, however, I am not convinced by any of the historical "calendrics" data. I find that ancient (nearby) historical "dates" DO NOT allude to ANY specific day of the week. So, (because this aspect is important to me) I was hoping there might be a more reliable way (specifically using astronomy) to attach a particular day of the week to that particular eclipse using some other astronomic event to calculate the "days" from. $\endgroup$
    – user22542
    Aug 21 at 23:45
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    $\begingroup$ The days of the week are very simple. So is the Julian calendar. The eclipse occur at a certain time. That time can be called "14 April 32" in the Julian calendar. What would it take you to be convinced? It is possible that the Ancient people miscounted and got their calendar wrong. It is possible that they wouldn't have called that day a "Monday". But that would be their mistake. If the 22 aug 2021 is a Sunday, then the eclipse happened on Monday the 14th April 32 in the Julian calendar. $\endgroup$
    – James K
    Aug 22 at 0:31
  • $\begingroup$ No. Not so. Nothing is simple... The Julian "instant answer" link above placing the Julian day on Monday on Apr 12 is a prime example. My motivation - Simply put - was from when I asked someone on SE a while ago about three separate eclipses and was told (apparently from looking at an eclipse panorama) that "by the way - all of those three eclipses occur on a Monday". I also looked at Josephus and many Wikipedia pages, but alas few historical references state THE DAY OF THE WEEK when something occurred - even though the 7 day week is a quite an ancient concept... all calendars are man made... $\endgroup$
    – user22542
    Aug 22 at 10:19
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Short Answer:

April 14 in the year now called 32 CE was certainly a Monday. Romans used the Julian calendar then so they would have called it April 14, in the year of the Consulship of Cn. Domitius Ahenobarbus and L.Arruntius Camillus Scribonianus, and sometimes AUC 785. But the Romans didn't use a seven day week yet, and so they wouldn't have recorded it as Monday.

The Jews did use a seven day week, and would have recorded April 14 in 32 CE as the second day of their week, the equivalent of the modern Monday. But which day number, month, and year in the Hebrew calendar corresponded to April 14 32 Ce is a more complicated question, depending on how closely the dates in the Hebrew calendar in 32 CE corresponded to the dates in the modern Hebrew calendar calculated backward in time to 32 CE.

I don't know if anyone knows enough about the ancient Hebrew calendar to say what Hebrew date would have been used on April 14, 32 CE.

Long Answer:

The question states that there was a total lunar eclipse on April 14, 32 CE.

Therefore user 22542 must have information that:

One) A total lunar eclipse was observed by one or more ancient persons and recorded in one or more ancient calendars on a date converted into April 14, 32 CE.

Or:

Two) Modern astronomers have calculated there was a total lunar eclipse visible on April 4, 32 CE in the Julian calendar.

And possibly if user 22542 said what his source for the eclipse was it might help persons trying to answer.

The Julian calendar was established at the order of Gaius Julius Caesar in the year which is now known as 46 BC, and began use on January 1, 45 BC.

So government and military officials everywhere in the Roman Empire would use the Julian calendar to record events, possibly alongside ether, local, calendars, by AD 32,or 32 CE.

The question is concerned with the Hebrew calendar.

In 32 CE there were Jewish communities scattered over a vast region, as far west as Portugal and Morocco, and at least as far east as India, I guess. But I beleive that the largest concentrations of Jews were in Palestine in the Roman Empire and in Mesopotamia in the Parthian Empire. They would use the Hebrew calendar for some purposes and the Roman and other calendars for other purposes.

I note that those lands are spread out over about 7 or 8 hours of local time differences.

I also note that different timekeeping systems begin and end days at different times of day. So time systems make a day go from midnight to the next midnight, others from dawn to dawn, others from noon to non, and others from sunset to sunset., and others from the calendar.

And of course different calendars begin years at different months and days.

The Julian calendar has a simple system of adding a leap day every four years. But at first there was a problem.

Although the new calendar was much simpler than the pre-Julian calendar, the pontifices initially added a leap day every three years, instead of every four. There are accounts of this in Solinus,[45] Pliny,[46] Ammianus,[47] Suetonius,[48] and Censorinus.[49]

The problem was discovered, and leap years were not used again for seveeal years until the dates were correct again.

Different chronologists claim that the first year in the normal and uninterrupted sequence of leap years every four years was 4 CE or 8 CE. Since then there has been a leap year every four years in the Julian Calendar.

The cycle of days of the week is extremely simple. There are only seven day names and they occur in the same order, over and over again. I note that the major monotheistic religions make specific days of the week, Friday, Saturday, and Sunday, holy days, so keeping track of the days of the week is both important and easy for members of those reliigons.

The seven day week originated in Mesopotamia by about 2000 BCE.

A continuous seven-day cycle that runs throughout history without reference to the phases of the moon was first practiced in Judaism, dated to the 6th century BC at the latest.[15][16]

https://en.wikipedia.org/wiki/Week#Ancient_Near_East

So any event which happens on a Monday in English speaking countries happens on the second day of the week in the Hebrew calendar.

So it is really simple to calculate that April 14, in the year that later became known as 32 CE, was a monday in the Julian calendar, and that the Julian calendar was used by Romans in that era, although they didn't use a seven day week yet. And jews would consider Monday, April 14, 32 CE to be the second day in the their 7-day week cycle.

But what was the date of the actual physical eclipse recorded in the Roman, Hebrew, and other clanedars?

And what month and year was Monday, April 14, 32 CE in the Hebrew calendar as used in 32 EC?

As I remember, the Roman calendar was a lunisolar one, added leap months every few years, instead of leap days, before the Julian calendar reform. And the priests were in charge of doing so. And being a member of priestly order was a normal part of the career of a Roman politician. So the priests often omitted adding leap months in the years wwhen their political foes were in office, and added leap months to years when their political allies were in office, without caring about calendar accuracy. So the Roman date was several months off of what it should have been by the time of the Julian calendar reform.

The Hebrew calendar is also a lunisolar calender and has leap months added very two or three years to keep it in line with the seasons.

The present Hebrew calendar is the result of a process of development, including a Babylonian influence. Until the Tannaitic period (approximately 10–220 CE), the calendar employed a new crescent moon, with an additional month normally added every two or three years to correct for the difference between the lunar year of twelve lunar months and the solar year. The year in which it was added was based on observation of natural agriculture-related events in ancient Israel.1 Through the Amoraic period (200–500 CE) and into the Geonic period, this system was gradually displaced by the mathematical rules of the Metonic cycle used today. The principles and rules were fully codified by Maimonides in the Mishneh Torah in the 12th century. Maimonides' work also replaced counting "years since the destruction of the Temple" with the modern creation-era Anno Mundi.

So the exact form of the Hebrew calendar used today dates back to about 1170-1180 CE. And the farther back in time a Hebrew calendar date was recorded, the more and more likely it would be for there to be a difference from the proleptic date calculated from the modern calendar rules.

I note that in 32 CE the Hebrew month begans with observation of the new cresent moon, which of course would appear close to the Sun in the sky. And the Hebrew calendar day begins at nightfall. So a month might be declared to have begun on different days in different longitudes. And local weather condiditons could affect whether the new moon was visible on a specific day.

April 14 in the year now called 32 CE was certainly a Monday. Romans used the Julian calendar then so they would have called it April 14, in the year of the Consulship of Cn. Domitius Ahenobarbus and L.Arruntius Camillus Scribonianus, and sometimes AUC 785. But the Romans didn't use a seven day week yet, and so they wouldn't have recorded it as Monday.

The Jews did use a seven day week, and would have recorded April 14 in 32 CE as the second day of their week, the equivaent of the modern Monday. But which day number, month, and year and year in the Hebrew calendar corresponded to April 14 32 CE is a more complicated question, depending on how closely the dates in the Hebrew calendar in 32 CE corresponded to the dates in the modern Hebrew calendar calculated backward in time to 32 CE.

And I don't know if even the greatest experts in the ancient Hebrew calendar can answer with certaintly.

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  • $\begingroup$ Thanks for all of the eclectic historical info. , but I have already concluded that the Torahcalendar resource that I was using is very consistent with the (data supported) contemporary Julian calendar days and dates (see my edits added above). However, if you happen to know anything about reading Saros-Inex Panorama data for "day of the week" eclipse correlations, that sure would be appreciated. Here is the link to the NASA eclipse panorama web page - eclipse.gsfc.nasa.gov/SEsaros/SEpanorama.html $\endgroup$
    – user22542
    Aug 23 at 8:40

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