by Heribert Illig

[This is an English translation from April 1991 by Birgit Liesching of the first article on the medieval phantom time published in Vorzeit-Frühzeit-Gegenwart 1/1991, also available in German on this website.]

The quintessence of this article is as simple as it is far-reaching:

Between the time of Caesar and Modern Times, our chronology carries about 350 years too many.

This discovery results from a simple calculation and the vain attempts of earlier scholars to change their wrong result to a right one. The Gregorian Calendar continues the Julian; our calendar1, therefore, links Antiquity and Modern Times, it includes the Roman Imperial Era as well as the entire Middle Ages. If the new calendar has been erroneously grafted on to the old one, then all dates and synchronisms between the time of Caesar and the Early Renaissance will have to be reviewed.
A reminder: In -442, Pontifex Maximus Gaius Julius Caesar introduced the Julian Calendar, which was named after him, and in which every fourth year had 366 days instead of 365. This calendar was so good that a correction was only required 1626 years later. Pope Gregory XIII felt obliged, in 1582, to have the calendar brought back into harmony with the astronomical seasons. This was done by skipping ten days in the counting of the dates: 4th October 1582 was followed immediately by 15th October 1582. In order to avoid for the future a drifting apart of the calendar and the movement of the Earth around the Sun, the leap year rule was, moreover, refined. So the Gregorian Calendar is basically only a corrected and improved Julian Calendar. Whereas the Julian year showed a difference to the tropical year of 674 sec = 11 min + 14 sec, the Gregorian year gets as close as 26 sec to the tropical year and is therefore safe from corrections for millennia.

Julian year: 365.2500 days = 365 d 360 min = 365 d 21,600 sec
Gregorian year: 365.2425 days = 365 d 349 min 12 sec = 365 d 20,952 sec
Tropical year: 365.2422 days = 365 d 348 min 26 sec = 365 d 20,926 sec

The New Encyclopedia Britannica (1985) says under the heading “Calendar” on the subject of the Julian Calendar, which was used for the following approx. 1600 years:

“During that time, however, the disagreement between the Julian year of 365.25 days and the tropical year of 365.242199 days gradually produced significant errors. The discrepancy mounted at the rate of 11 minutes 14 seconds per year until it was a full ten days in 1545, when the Council of Trent authorized Pope Paul Ill to take corrective action”.

This correction was only carried out 37 years later under Pope Gregory XIII.

But this simple multiplication gives a wrong result:
1626 years with an annual discrepancy of 674 sec results in 1,095,924 sec or, a day having 86,400 sec, approx. 12.7 days.

In 1626 years the Julian Calendar was slow by 12.7 days. As a correction was only possible in entire intercalary days3, it would have been necessary, in 1582, to jump over 13 days (this is confirmed by Zemanek, 1984, p.126). In fact, however, only 10 days were cut out.

Having quoted the opinion of the Encyclopedia Britannica as representing that of numerous other works, an explanation must be found for this serious mistake. There are four possibilities to explain why the correction of 1582 came out clearly lower (some 20 %) than indicated by the calculation:

  1. the Papal Romans did not relate their correction to Caesar’s correction,
  2. the Romans of antiquity had not determined the vernal equinox correctly,
  3. the Papal Romans determined the vernal equinox differently from Caesar’s astronomers,
  4. there were fewer than 1626 years between Caesar’s and Pope Gregory XIII’s reforms.

Re 1) The Romans of the 16th Century AD

When a calendar slowly drifts, a correction should bring it back to its original astronomical situation. One therefore tends to agree with the Encyclopedia Britannica. There is, however, an alternative in the specialist literature:

As the date of the equinox at the time of the reform had moved away from the real one by ten days, i.e. it fell on 11th March instead of 21st March, the date was to be advanced “to the equinoctial day XIIth Calendae Aprilis = 21st March of the year 325 (Council of Nicaea) (Ginzel, 1914, III, 257).

This reference to the first Council of Christendom would be an explanation for the discrepancy queried above of 2.7 or 3 full days, because the calculation for the 1257 years passed between Nicaea and Gregory XIII indeed results in 10 compensation days:

1257 years with an annual discrepancy of 674 results in 847,218 sec or, a day having 86,400 sec, approx. 9.8 days.

So one would have to assume that in 1582 the calendar was not related to that of Caesar, but that of the Council of Nicaea. An Abbé describes what is supposed to have happened: the experts agreed by “finally declaring they preferred to suppress 10 days in order to bring the equinox forward to the 21st of March where it had been since the Council of Nicaea. This was to show respect to the Council and to bring as little change as possible into the liturgical books which had been revised by Pius V [Gregory XIII’s direct predecessor]“ (Chauve-Bertrand, 1936, p.89).

It should be added that for all makers of calendars, including Gregory’s scholars, there were two possibilities for correction: either the calendar remained unchanged, in which case the astronomical equinox had to be given a new calendar date, or the equinox kept its calendar date, then the calendar had to be corrected. In more concrete terms: either the equinox no longer fell on 21st March, but on the 11th — or 10 days had to be jumped over in the calendar to ensure that the equinox again fell on 21st March. In 1582, it was decided to correct the calendar and to adjust 21st March. In 325, according to this theory, it was decided to adopt a new equinoctial date, which is the one valid now, namely 21st March instead of previously 25th March (see below).

The Council of Nicaea

The early Church attributed an importance to Easter which is difficult for us to understand. In 325, there were not only disputes raging around Arian teaching, but there were real political parties fighting for a single Easter date for the entire Church. In trying to separate the highest Christian festivity from the Jewish Passover (which is always celebrated at the time of the first full Moon in spring), Protopaschites fought with Quartodecimians, and later Audians and Novatians joined in as well.

Finally, the Council “decided that Easter, which until then had been celebrated at different dates by Christians in Asia Minor and in Europe, was to take place from now on the first Sunday after the 14th day of the Moon (which, roughly, corresponds to the full Moon) on or after the beginning of spring: the date of the beginning of spring was set on 21st March” (Moyer, 1982, p.94).

This sounds plausible, but not necessarily true. “The wording of the acts of this Council regarding Easter is not known, but the letter from the Nicaean Synod to the Alexandrine Churches and Libyan Bishops is preserved, as is the letter which Emperor Constantine had circulated immediately after the Council among those who had not attended the Council” (Ginzel, 1914, III, pp.216f — emphasis added). But Ginzel points out that neither of the two letters contains a ruling for the determination of Easter or the date of 21st March for the vernal equinox4; they only mention the need for unity over the date of Easter (ibid.).

That there cannot have been much unity is proven by the fact that after the Council of Nicaea, the custom of the free Easter date was introduced.

Faithful Christians seemed to think for a while it that would have been according to God’s plan that Christ should have died on the anniversary of his conception, i.e. on the day of the “Annunciation to Mary” (25th March), nine months before Christmas (not at all the day of “Immaculate Conception”, as this expression concerns the conception, free from original sin, of Mary on 8th December, nine months before the birth of Mary, on 8th September). This date of 25th March fixed Easter in the calendar and defined it as the immovable start of the year (Ginzel, 1914, III, p.164).

In fact, the Church only achieved a single Easter date in the 5th century; the reference point for the first spring full moon was the vernal equinox (Ginzel, 1914, III, p.252)5.

This confirms the suspicion that a decision regarding the calculation of Easter and the date of the equinox was not taken at Nicaea. This Council is only supposed to have regulated the exact and definite Easter date, because the totally indubitable 10 compensation days skipped in 1582 refer to the year 325, but not -44.

Even more has been insinuated regarding this Council although, or because, we know so little about it, because “minutes were either not kept or the Church made them disappear” (Deschner, 1980, p.394). But the Abbé Chauve-Bertrand reports that the Council Fathers knew as early as 325 that the Julian Calendar was adrift. For this reason they not only fixed the Easter date and the beginning of spring, they also newly fixed the beginning of spring. According to him they decided on the opposite solution to the Gregorian reformers, leaving the calendar dates and moving the vernal equinox forward from 25th March to 21st March (both Julian) (Chauve-Bertrand, 1936, p.87).

All the foregoing is pure speculation:

  • The wandering motion of the vernal equinox was mentioned for the first time in 1200 in a document by Master Chonrad; a very first hint is known from the 8th century, when Bede calculated his Easter Table until 1063 and remarked that the full Moon sometimes appeared earlier (Ginzel III, p.252),
  • the date of 25th March was gained by simple retrocalculation, because moving the vernal equinox from 25th March to 21st March means three skipped days — this calculation is perfectly correct for the 369 years between Caesar and the Council of Nicaea:
    369 years with an annual discrepancy of 674 sec results in 248,706 sec or, one day having 86,400 sec, approx. 2.9 days.
  • Chauve-Bertrand took over the date of 21st March for the vernal equinox from the Gregorian reform.

Precisely because there is not sufficient evidence as to the calendar day on which fell the vernal equinox of the year 325, it must be retrocalculated. Ginzel did that himself: “The correct astronomical entry into the vernal equinox in the year 325 was on 20th March 12 h 44 min Roman time, in the year 1582 on 11th March 0h 48m Roman time (counting the day from midnight to midnight)” (Ginzel, 1914, III, p.257). If this calculation was correct, then there would only have been a requirement of 8.5 days or 9 full days to be compensated between Nicaea and Gregory XIII. Whether he included in his calculation that the length of the tropical year decreases due to the slowing-down of the Earth’s rotation, so that the error in the Julian Calendar grows even faster than he imagined (Moyer, 1982, p.96) is impossible to guess from his result.

One should, however, not demand too much from this first Council, as it was the only one in which the Holy Ghost was unable to give sufficient support — because he achieved his divine status only in 381 (Deschner, 1980, p.384).

Re 2) The Romans of the -1st Century

Is it possible that the Ancient Romans were unable to accurately determine the equinoxes, i.e. the East-West direction? The question sounds absurd since the required knowledge is said to have been available for more than 2000 years at the time of Caesar. Its visible proof is the Pyramid of Cheops, the incredibly precise orientation of whose base lines according to the cardinal points has always been admired. Even if meanwhile the -6th century is considered to be the time of its construction (Heinsohn/Illig 1990, p.115), the Romans would have had 500 years to learn Egyptian measuring methods. That they did in fact learn this lesson in good time can be shown on the inimitable sundial of Augustus.

On the Field of Mars in Rome, the first Emperor ordered to erect a subtly calculated combination of victory monument, birthday memorial, mausoleum, peace altar and sundial, the like of which is not known to have been built anywhere else in the Occident. Only the mausoleum is still on its original spot, the Ara Pacis and the obelisk have been displaced and there are only fragments of the network of lines to be found, deep below today’s street level. Quite recently, Edmund Buchner was able to reconstruct the entire set-up and evaluate it archaeologically (Buchner, 1982).

Augustus wanted to document his victory over the Egyptians by setting up an obelisk, the first one to have been brought all the way from Egypt. In the year -12 (ibid., p.48) the 50-year-old emperor decided, to use it as a gnomon, nearly 30 m high, the pin of a sundial whose network of lines, made of marble, was to cover a surface of more than 160 x 75 m. The Peace Altar (Ara Pacis) which was also ready and consecrated in -8, and the mausoleum, which had been erected previously, were of astronomical-astrological relevance.

The Emperor himself had been born precisely at the moment of the autumnal equinox. “On the Emperors birthday … the shadow wanders from morning to evening for about 150 m along the dead straight equinoctial line, precisely to the middle of the Ara Pacis; there is, thus, a direct line from this man’s birth to Peace which visibly demonstrates that he was “natus ad pacem” (Buchner, 1982, 37).

In order for this phenomenon to occur, the equinoctial line must run perfectly straight from West to East.

If it was possible, at that time, to orient the course of the shadow so accurately according to the equinoxes, then we can assume, with very high probability, that one generation earlier, at the time of Caesar, the determination of the equinoxes would not have caused any difficulties either. This means, however, that the vernal equinox in Rome fell on the same day it does now, i.e. 21st March (Gregorian, though!).

Re 3) The Spring Equinox

The Ancient Romans, therefore, were able to determine the equinoxes very accurately. The close link between equinoxes and calendar is also proven by the sundial of Augustus.

In Caesar’s time, the beginning of spring was not yet fixed at the date of the vernal equinox. Only in late antiquity were the seasons linked with solstices and equinoxes (Buchner, 1982, p.79), in earlier times summer was extended, due to climatic factors, to five or more months. For this reason we know neither of Caesar nor of his contemporaries on what day of their calendar their vernal equinox fell. Columella and Pliny later calculated 24th March, a date which Ginzel describes as incorrect and which he corrects to 23rd March (Ginzel, 1911, II, p.285). Moving from 23rd March (Caesar) to 21st March (Nicaea), however, only demands one compensation day to be skipped, which would mean that there were only around 130 years between Caesar and Nicaea.

But we have another contemporary date which renders these retrocalculations and corrections superfluous: all the authorities agree that the birthday of Augustus was on 23rd September, with which they mean a Julian date, as confirmed by Bickerman (1980, pp.48f). Augustus, however, was born in -62 and thus before the Julian calendar reform of -44; his birth date, therefore, had to be recalculated in antiquity to give a Julian date. This fact makes this date particularly interesting.

The recalculation was inescapable because Caesar’s calendar reform had to give the year -45 a total of 445 days in order to bring the calendar in agreement with astronomical reality (Ekrutt, 1972, p.51). In the case of Augustus, it was impossible to make a mistake because his birthday fell precisely on the date of the autumnal equinox. Whether the recalculation is correct or whether the date of the autumnal equinox was simply chosen, one fact is certain: 23rd September is the date of the Julian autumnal equinox in the -1st century.

But the Gregorian autumnal equinox, too, is on 23rd September, as a glance at a calendar for 1991 will confirm. This leads to the inescapable conclusion that the Gregorian Calendar, which has fixed the beginning of autumn on that day since 1582, restored precisely the situation where the Julian Calendar was at its introduction.

Corresponding to the Gregorian beginning of autumn on 23rd September there is a beginning of spring on 21st march, as can again be seen in the calendar for 1991; this relationship is always valid. We can therefore be sure that at the time of Augustus (and therefore the time of the Julian calendar reform in -44) the vernal equinox was on the 21st March — originally Julian, but also from the Gregorian point of view.

The Gregorian Calendar Reform, therefore, restored the calendar situation obtaining in -44, at the time of Caesar’s reform. This totally contradicts the statement that in 325 the beginning of spring was on 21st March Julian, because the 369 years between Caesar and Nicaea must, as we have shown above, have led to a shift of 2.9 or 3 full days; the “slow” Julian Calendar would, after approx. 350 years, show the equinox on an earlier calendar day.

Chronologists have, nevertheless, found a way to lay two opaque veils over this absolute incompatibility, which has enormous consequences. The first has already been mentioned: in many current presentations (cf. above, quote from Encyclopedia Britannica) it is suggested that of course the Gregorian Calendar restored the astronomical situation at the beginning of the Julian Calendar. He who calculates this for himself and finds that 10 skipped days were not sufficient, is given the supplementary information in specialist literature that of course only the situation of Nicaea was restored.

‘The beginning of spring in Caesar’s time (actual) and Nicaea (postulated) therefore both fall on 21st March, though between both dates there should be a full 3 days: if it was 21st March at the time of Nicaea, Caesar’s date would be 25th March, at the most 24th March.

E.J. Bickerman, under “practical suggestions” spreads a second veil: “In ancient (and medieval) chronology we use the Julian Calendar and not the Gregorian which is used now. Both coincide c. AD 300; but then the Julian dates run behind the Gregorian Calendar by three days every four hundred years. In the reverse direction, from c. 100 BC, the Julian year is in advance of the Gregorian Calendar by three days every 400 years, so that, e.g., 29 December 102 BC (Gregorian) was already 1st January 101 BC” (Bickerman, 1980, p.89).

In this statement, Bickerman first confirms that the 10-day correction carried out in 1582 only reaches back to the Council of Nicaea, as this is the only way to explain why both calendars agree around AD 300. Then he says that after AD 300 and before 99 BC the calendars are drifting apart with a deviation of 1 day per 133.3 years (400 : 3). This value is useful as a rough guide, the correct figure is close to 128.2 years (86,400 sec : 674 sec).

But between -99 and +300, Bickerman creates a mysterious interval of 400 years in which both calendars are said to be totally synchronous. This is, of course, impossible: the cosmic clockwork shows, inexorably, a calendar difference of one day for every 133 (or better still, 128) years. If the Julian and Gregorian Calendars agreed around AD 300, then the Julian Calendar must in 172 have been in advance by one day, in 44 by 2, and in -84 by 3 days (which does not take into account that due to the rounding-off of full days the calendar would have been advanced in 236 by one day, in 106 by two, in -18 by three). A standstill period can only be considered to have existed if full days are taken into account and even then only for a maximum of 128 years.

This shows that Bickerman’s interval is meant to conceal a weak spot. If someone has accepted the rule of thumb whereby movements up and down happen within a 400-year period, then he may perhaps also accept the 400-year interval in which there is total standstill. Such a standstill period would then suggest that the vernal equinoxes of the time of Caesar’s reform and the Council of Nicaea, between which there lies a period of 369 years, could have fallen on the same 21st March6.

These two veils hide the false seam which holds together the Julian and Gregorian Calendars in a way that falsifies history: the alternating reference of the Gregorian reformers to either Nicaea or Caesar silences the questioner who does not understand the matter, whereas those who insist further are asked to be satisfied with the standstill between Caesar and Nicaea. But this deception need not be deliberate: chronologists of the 16th to 20th centuries, who did not doubt the course of history, had to cope with the problem that by 1582 the calendar had become slow, astronomically speaking, by 10 days but should, in relation to Caesar’s correction, have been slow by 13 days. As stating the truth would have thrown entire centuries into Orcus, they used the veil.

Re 4) The New Past

Dark Ages which never existed are well-known from antiquity. They were introduced in both Greek and Egyptian histories to account for the lack of synchronism between them and Biblical history (in this context, cf. Heinsohn, 1988, Illig, 1988, as well as Heinsohn/Illig, 1990, in each case passim). In analogy to this there are, between the end of antiquity and the High Middle Ages, so-called dark ages, which are called precisely the same as those of the pre-Christian Era, and which at present are being looked at again (e.g. by Wood, 1982/88, with his “Search for the Dark Ages”).

We can, therefore, start a new calculation with a clear conscience. On the basis that the 10 skipped days really compensated the time discrepancy between Gregory and Caesar, as is being suggested, these ten years are the surest indication as to how many days separate Gregory XIII from the date when Caesar introduced his Julian Calendar:

10 days : 674 sec deviation/year = duration of calendar period. (10 x 86,400 sec) : 674 sec = 1281.899 years.

This means that the Julian Calendar had run for approx. 1282 years to accumulate a discrepancy of 10 days with regard to the solar year, or that Caesar introduced his calendar not 1626, but 1282 years before Gregory XIII, 345 years later, in the year of the Lord 300!

As, however, the calendar can only be corrected by full days, the correction of 10 days can indicate an observed deviation of between 9.5 and 10.5 days. This uncertainty of an entire day, means:

86,400 sec : 674 sec = 128 (years of uncertainty interval)

The end result: Caesar carried out his reform 345 +/- 64 years later, i.e. between 281 and 409 years later. In the Christian Era this interval lies between the years AD 236 and 364, with the average figure around AD 300.

If the premises of this calculation are corrects, from 281 to 409 years have to be eliminated from the Christian Era between Caesar and Gregory XIII.7

The Consequences

At this point, at the latest, innumerable questions are raised. Only three shall be dealt with at present.

Where can the 300, 400 or maybe even more years be eliminated from the interval between Caesar and Gregory XIII?

Some first indications are given in the present publication. Until at least 300, the Roman Imperial Era seems to be so solidly constructed that it is unlikely to find gaps in it. The same applies for the period starting with Early Renaissance. This search is thus limited to the late Imperial Era and the Middle Ages. It is not expected that several centuries can simply be cut by distributing their (scarce) relics over the period before and after.

Medieval chronology is based on different sources which were combined in a synopsis only later: Byzantine history, Papal history, Frankish traditions, Celtic island memories, Gothic historiography, other traditions from the period of the peoples’ migrations, Islamic traditions, etc. In order to take all these synchronisms into account, it is possible that at various times “islands in a vacuum” were created. A comparable occurrence is known from the various countries of the ancient world. G. Heinsohn has shown that there are consistent gaps lasting 1500 years (Indus Valley, Central Asia, Iran, Southern Mesopotamia) and that in Northern Mesopotamia, too, two smaller gaps were created because there are links with two unsynchronized chronologies for the Mitanni= Medes (Heinsohn/Illig, 1990, p.306).

Why would such a serious mistake have been made, and why would it not have been exposed?

Further references to the falsification of a non-existing past are to be found in H.U. Niemitz’s article in this journal. Lincoln/Baigent/Leigh, too, showed (1984) that usurping rulers (such as the Franks) might have had great interest in creating a better past after having overcome their kings (Merovingians). However, someone who created a better past had to ensure that in future, too, everything remained unchanged.

How was it possible to pin a new past on the European population? Was their memory so weak?

At the present moment it is impossible to judge how quickly confusion — and the confusing movements of many peoples are not necessarily to be eliminated — could have led to an extensive loss of history for populations, some of whom may have been quite newly formed. In any case neither the Middle Ages nor the early Modern Times had an uncorrupted knowledge of chronology.

We tend to think that the Gregorian Era is observed worldwide, and may be surprised to learn that our year 1991 is the year 5751 for the Jews, for the Muslims it is 1410 (approx., due to their lunar calendar). At the time of Dionysius Exiguus (535) the known eras included the Byzantine Era (6043), Era of Panodorus (6027), Ab urbe condita (1288), Era after Pul (1281), Era of Augustus (564), and the Era of the Martyrs (251). The introduction of the Gregorian Calendar was not abrupt and uniform in Europe but lasted from 1582 in Italy to 1927 in Turkey, the calendars running parallel during these three-and-a-half centuries.

Moreover, there were local deviations: until Napoleon’s invasion, Venice started the year not on 1st January, but on 1st March; Florence and Pisa started theirs on 25th March, but a year out. Until the year 1749 it was possible to include one and the same day in three different years, depending on whether one was in Pisa, Venice or Florence (Ginzel, 1914, III, pp.160f). In this jumble of figures, the general public had to rely solely on conversions presented by the specialists. Calendar makers, therefore, were in a perfect position to manipulate, consciously or unconsciously, when converting one calendar into another.


1) Further criteria for testing calendars
Continuous lists of rulers would supply such criteria. But neither the series of more than 250 Popes nor the sequence of Byzantine Emperors appear so irrefutable as to enable the absolute correctness of the chronological axis to be deduced from them.

The current Era since the birth of Christ alone cannot serve, for this anchor point was for the first time used by Dionysius Exiguus in 532, after the period of Antiquity as such. The popes did not take this over very quickly, anyway: not till the 10th century, had John XIII had first documents dated AD, without, however, abolishing the official Era of Martyrs. The Christian Era can only be shown to have been used regularly after 1431 (Ginzel, 1914, III, p.181).

The famous calculation of the precession used by astronomers and astrologers is not suitable, either. In the -2nd century, Hipparchus discovered that the sign of the Zodiac which rises at the beginning of spring does not always remain the same. Each of the twelve signs in succession moves into this position, after approx. 2160 years each. This is due to the movement of the Earth’s axis: not only is it tilted, it also moves around in a slow circle. In the course of roughly 26.000 years, the Platonic great year, it completes one full circular motion.

However, with all the fuss people are making about the change from one sign of the Zodiac to the other — at the moment we are moving from Pisces to Aquarius — the relevant figures are imprecise and contradictory. One of the reasons for this is that each of the signs of the Zodiac takes up a different amount of space in the sky. But even astrologers who have divided up the Zodiac into twelve equal parts of 30° are unable to agree on precise moments of change and prefer talking of broad overlapping zones.

2) Year-Dates with Minus Signs
The year-dates as used in this journal, with minus signs for years BC, follow a precisely defined astronomical practice which has not, so far, been used accurately. The calendar according to the Christian Era lacks the year zero which, however, is necessary to be able to calculate sums and differences quickly. For this reason, astronomers have declared the year 1 before the Birth of Christ to be the year 0, year 2 BC the year -1, and so forth. Year 45 BC is, therefore, the year -44. Until this issue, we would have simply written -45, because this difference of a year is irrelevant in considerations concerning some much greater uncertainties. As, however, it can be decisive in the present context, all the figures in this paper given with the minus sign will have to be increased by 1 to yield the correct BC date.

3) Calendar Correction by Way of a Leap Year
Building a calendar is an attempt to convert the actual, observable solar year into a scheme in such a way that there is not the slightest divergence between scheme and celestial motion, because each difference develops, in the course of the centuries, to a gaping hole. The chief problem lies in the fact that the solar year (or tropical year, defined as the period between two subsequent passages of the Earth through the vernal equinox) cannot be expressed in entire days. At the end of the year, only about a quarter of the last day belongs to the old year. It took long for this problem to be solved by adding intercalary days which are added at certain intervals. (Entire months are required when, as with the Muslim and Jewish calendars, the lunar year with 355 days and the solar year with approx. 365 days are to be harmonized. It is unlikely that the revolution around the Sun ever corresponded to a complete number of days — no Sun-related calendar, therefore, can have been valid for a long time without a ruling concerning intercalary days.)

4) The vernal equinox
For the Christian calendar makers of the 16th century, the most important problem consisted in linking the astronomical vernal equinox again with the first day of spring, because the following first full Moon was decisive for the Easter date of the ecclesiastical year. The observation everyone was able to confirm for themselves, that Easter was drifting towards summer, emphasized the need to correct the calendar.

The vernal equinox is so called because on that day, in principle, the Sun rises at 6 a.m. and sets at 6 p.m.; day and night are, therefore, of equal length. Furthermore, this is the moment when the Sun rises precisely in the East, an important phenomenon for determining the cardinal points (this is only the case on one other day, the autumnal equinox). Finally, it is also fixed astronomically:
Due to the Earth’s axis being tilted, an observer standing on Earth lacks certainty. In addition to the plane of the Earth’s revolution around the Sun, which is described as the ecliptic (which is the apparent path of the Sun in the sky), there is the second plane of the celestial equator (the projection of the Earth’s equator onto the celestial sphere). The points of intersection between ecliptic and celestial equator are the vernal and autumnal equinoxes. The Gregorian reform fixed the vernal equinox at 21st March. Since we have to use a calendar with leap days and as this leap day is introduced just before 21st March, on 29th February, the vernal equinox falls more often on the 20th March than on the 21st, on rare occasions even on 19th. This does not, however, change anything about the principle according to which it is fixed (Moyer, 1982, pp.94, 99).

5) Calculation of the Easter date
The disputes went on for much longer. Agreement between the Celtic and Roman churches was only reached in 663 at the Synod of Whitby. Until then, the Celts in the British Isles, but also on the Continent, calculated Easter according to an 84-year cycle which was recognized in 314 at the Council of Arles. “The Alexandrians, however, preferred the more precise 19-year cycle, which was taken over by Pope Leo I and all Roman churches in the middle of the 5th century” (Cunliffe, 1980, 193). These traditions are in noticeable contrast to the definitive decisions which were supposed to have been taken at Nicaea in 325. When was the calculation of the Easter date really standardized?

6) Conversions Gregorian – Julian
Bickerman’s veil is luckily an exception, but the classical tables, such as Schram’s, 1908, also use this basic rule of one compensation day every 400 years. It was, and still is, practiced (Zemanek, 1984, p.126) because “the Gregorian Calendar is not generally back-calculated” (Schram, 1908, XVI). For this reason Schram permits his tables, which are otherwise precise to the day, not accurately to reflect the back-calculation — a further veil to be drawn. Schram shows for Gregorian 21st March -44 (the year of Caesar’s reform) the Julian date of 23rd March, but Grotefend (1891, p.90) seems to think that it ought to be on 25th March. In 1984, Zemanek seems to have gone back to Schram, for “originally on 23rd March, the vernal equinox had moved forward to 11th March. It was fixed on 21st March, which made it necessary to skip 10 days” (Zemanek, 1984, p.29). The constant changes in dates, i.e. the further uncertainties shown, are a sure indication of a weak point.

Today’s computer programs, like the old tables, go back to the “Julian calculation”. It was developed in the year after the Gregorian reform by Joseph Justus Scaliger (1540-1609) and is very simple: starting with 01.01.4713 BC, every day is given a consecutive number and is, therefore, unequivocally identifiable. But the calculation from a calendar day to this “Julian day” (which is nothing to do with the Julian Calendar) is made via the Gregorian correction factor and this, again, follows the old rule (Zemanek 1984, p.124).

7) To be on the safe side, we want to admit that in the action of “pruning calendars” there may have been a discrepancy of up to a day, so that the interval to be taken out lies between 217 and 473 years. According to this calculation, the maximum number of calendar years to be eliminated is 473.


Bickerman, E.J.: Chronology of the Ancient World (London, 1980):
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