Xe who postulates that Roman time is dendrochronologically dated 218 years too old, thus implying that there are about 200 invented years in the Christian era, also has to deliver some astronomical and archaeological evidence which supports that claim.
According to Wikipedia, astronomy is a natural science dedicated to the study of celestial objects such as stars, galaxies, planets, moons and nebulae, and their physics, chemistry and evolution, among other things. Astronomy is demonstrably one of the oldest sciences, as prehistoric cultures have left astronomical artifacts used for methodical observations of the night sky. However, the invention of the telescope was required before astronomy was able to develop into a modern science. Historically, astronomy has included disciplines as diverse as astrometry, celestial navigation, observational astronomy and the making of calendars.
Astronomy is one of the few sciences where amateurs still can play an active role, especially in the discovery and observation of transient phenomena such as eclipses of sun and moon. Astronomy used as a dating method for historical observations in e.g. old documents usually has an even higher resolution in time than dendrochronology, but it requires a number of prerequisites to be reliable. Firstly, there have to be observations which can be analyzed; as ancient observations are handed down through time, their reliability has to be scrutinized. Secondly, the models used for retrocalculation of eclipses and other astronomical phenomena have to be sufficiently precise; the older an observation is, the greater the uncertainty.
Astronomers with a historical interest have spent quite a lot of job on connecting reported antique astronomical observations to retrocalculated astronomical events and to a high extent they claim that they have succeeded (see e.g. ref 1). A proposal to make any change in our chronology threatens to lay that work in ruins.
If we then maintain that our chronology is incorrect, but want to explain away a large group of seemingly correct observations we probably have to assume that the school that made the observations has somewhat by accident been correctly positioned on the time scale. That might e.g. be argued for the systematical observations of the Babylonian astronomers recorded on still existing clay tablets. A possible explanation might be that these to a high extent seemingly correct observations were registered according to a calendar that was not synchronized to our common AD calendar until after the introduction of the Christian era. That means they have never been synchronized towards the Roman "Ab Urbe Condita" (A.U.C.) calendar or to the list of Roman consuls. Because it is initially only the synchronization of our AD calendar against the West Roman time count which we dispute, however other time counts may prove to go the same way later on.
We are not educated in astronomy, but nowadays there are computer programs which allow to check if a reported constellation or eclipse of sun or moon really was visible at a certain place at a certain time. The program we used is the NASA Eclipse Web Site, which allows a detailed analysis of solar and lunar eclipses and supports the search for matching alternatives.
Initially, we had a look at dated astronomical observations made in the western part of the Roman Empire. There are quite a lot of solar eclipse reports but most are more or less imprecise, which means that it is hard to find any matching retrocalculated alternative at the proposed date. In fact, most seem to be "on demand observations" reporting solar eclipses e.g. when prominent persons died or in connection with a determining battle. But then we found four observations in Pliny's "Natural History" which apparently were made for scientific purposes and which were dated against the list of Roman consuls (we assume this list being trustworthy around Pliny's time). These observations had exactly matching retrocalculated alternatives at the proposed AD-dates. Was this the end of our hypothesis?
After the first chock we made a more systematical analysis of the case. Pliny's observations were no spectacular total solar eclipses, but ordinary partial solar and lunar eclipses which everybody can observe a few times during the own lifetime. We found with help of the NASA program that the reported special conditions occur several times per hundred years. Was there maybe a second alternative for Pliny's quadruple (his complete set of four timely coupled observations)? And indeed, there was an exactly matching second alternative 232 years later than that conventionally assumed.
232 years later is fully compatible with our 218 years dendrochronological error, so we were in business again and started to test our new 232-years-hypothesis. We found a spectacular alternative solution for Plutarch's total or annular eclipse of the sun from his "De facie quae in orbe lunae apparet" which made us convinced that we were on the right track. Then we found an alternative solution exactly 232 later for an eclipse of the setting sun reported by the Greek historian Xenophon (dated with the "Olympiad count" which is definitely synchronized with the Roman calendar). And there was more to come, e.g. a pair of astronomers, who were considered contemporary by their successors, but who now are separated by about 200 years because one of them made a unique observation which could be retrocalculated. With our hypothesis they would become contemporary again.
But we also found seemingly overwhelming proof for the correctness of complete collections of astronomical observations made in late antiquity. The most prominent collection is of course Ptolemy's Almagest, which in a very convincing way demonstrates that antique observation reports and modern retrocalculations are compatible. Or does it really? It has been disputed since long time ago if Ptolemy's own reports in the Almagest are made from real observations or if they are taken from some predecessor. Most modern astronomers having dealt with the case admit that Ptolemy's systematic errors are puzzling, their conclusions spanning from suspicion of some "fiddle with the truth" to the accusation of conscious scientific fraud.
If our dendrochronological results are true, we would indeed expect inconsistencies in the Almagest. The existence of two solutions for Pliny's quadruple, of which one confirms our calendar and the other one is compatible with our dendro results, also points at astronomy as the method chosen to inflate the Christian era. But who was capable to make such comprehensive retrocalculations? Without doubt the astronomical school of Alexandria in late antiquity. Maybe some Arabian astronomers in Medieval times. European astronomers not before Copernicus, i.e. in Renaissance. But at that time the AD count had already been in use for centuries and copies of the Almagest were widespread in Europe and the Islamic world.
If we assume that the prank originated from Alexandria, the most convenient point of time to manipulate the timeline would have been in connection with the "invention" of the Christian era. This theory would set the latest possible date to 525, the year which Dionysius Exiguus himself stated was the "present year" and "the consulship of Probus Jr.", as well as "525 years since the incarnation of our Lord Jesus Christ". But there is actually also an earlier "lastest possible date", which is 412 when Panodorus introduced the Alexandrian (Christian) era. This world era is synchronized with the Byzantine World Era and with the Roman year count in the same way as our Christian era, thus reaching in principle the same result as Dionysius Exiguus. If Dionysius Exiguus knew about Panodorus' synchronization has been disputed (ref.2).
This points even stronger towards Alexandria, which would eventually mean that the scientists of the most famous university in antiquity deliberately and knowingly for some reason made out that the West Roman past was 232 years older than it was.
What happened in Alexandria around 400? After having been famous for "pagan" philosophy and sciences, Alexandria had become a center for Christian theology. A lot of Church Fathers were living there at that time. Libraries were closed and destroyed, Theon, making astronomical observations in 364, was one of the last known scientists working at the Mouseion. In 391 all pagan temples were destroyed. Theon's daughter Hypatia was murdered by a Christian mob in 415.
In 367 the Bishop of Alexandria, Athanasius, defined which books should be included in the New Testament as we know it today. At about the same time, the gnostic gospels, giving a somewhat different interpretation of Jesus' life and death, had to go underground at Nag Hammadi. This means, in the true sense of the word, that a library of non-canonical books was sealed in a large jar and buried in the Egyptian soil until a farmer recovered it in 1945.
Here is not the place to speculate about the reasons for a time falsification. If one likes conspiracy theories, the book of Baigent et al "The Holy Blood and the Holy Grail" (ref.3) would provide relevant reading. This book has been the inspiration source for Dan Brown's "The Da Vinci Code". However, none of these authors considers invented years between Jesus and his alleged descendents (the Merovingians), which actually would make their story more plausible.
Of the phantom time hypothesis of Heribert Illig, however, who considers 297 years between 614 and 911 as invented in Medieval times, only the actual existence of invented years is left. Illig and his group originally concluded this from another astronomical observation, namely that the Gregorian calendar reform possibly does not account for all the years said to have elapsed since the introduction of the Julian calendar.
And finally: why did Dionysius Exiguus "reinvent" the Christian era 113 years after Panodorus? Maybe his mere intention was to discredit and delete an already existing Christian year count which he defines as the Era of Martyrs beginning with the first regnal year of Roman emperor Diocletian. As he stated in his Easter Tables: "... we did not wish to include in our circle the memory of an impious and persecutor, but we chose above to mark the time from the year of the incarnation of our Lord Jesus Christ." However, the Era of Martyrs survived and is today still used within the Coptic Orthodox Church. It was in use as a Christian year count long before the AD count was introduced, and if we are right and there are invented years in our calendar, the starting point of the Coptic calendar is not at all the beginning of the reign of emperor and persecutor Diocletian, but maybe the death of Jesus Christ or perhaps the death of Mary, Jesus' mother. Also this piece of the jigsaw points directly to Alexandria.
Update 2016-03-05: Read our new research paper which summarizes most of our old astronomical finds and also discusses fresh conclusions.
References:
1. Stephenson F.R.: Historical Eclipses and Earth's Rotation, Cambridge 1997.
2. Mosshammer A.A.: The Easter Computus and the Origins of the Christian Era. Oxford Early Christian Studies. Xi + 474 pp (Oxford 2008). Read here.
3. Baigent M., Leigh R., Lincoln H.: The Holy Blood and the Holy Grail. London, Jonathan Cape (1982).
Suggestions for further reading:
* A. D. Lee, From Rome to Byzantium AD 363 to 565: The Transformation of Ancient Rome. Edinburgh history of Ancient Rome. Edinburgh University Press, 2013. Review and preview, read here.