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Trismegistos Calendar

Genesis and outlook

Trismegistos Calendar is an new section that came about as a result of Sofie Remijsen’s interest in the practical significance of Sunday for the early Christians. Sofie wanted to make her conversion lists public available, and Mark Depauw offered to do that in the framework of Trismegistos. Then the idea came to link the list of days to the dates in Trismegistos, and this how TM Calendar was born, initially for the period 800 BC - AD 800. Recent collaboration with the Altägyptische Kursivschriften (AKU) project in Mainz (and indirectly with other egyptological projects - see below) led us to expand the chronological scope to 3500 BC - AD 1000.

TM Calendar is beta only. We know there are still a number of inaccuracies to fix, most of which we hope to correct in July. Right now it should be seen as a tool to facilitate finding texts in Trismegistos starting from a chronological interest. We hope to work together with other projects such as PeriodO and GODOT to elaborate TM Calendar further.

Chronological background

Reigns and regnal years

The regnal years follow the Egyptian count: the second regnal year starts on 1 Thot after the accession of the new emperor. The first and last regnal years are therefore often incomplete calendar years. Because of the uncertainty of accession dates, there might be an overlap between the reigns of successive emperors.

For Ancient Egypt before the late pharaonic period (specifically before the 24th Dynasty), the information is based on a list resulting from work done in Leipzig by the Thesaurus Linguae Aegyptiae (TLA), with some modifications by the project Altägyptische Kursivschriften (AKU). This was compiled by Lutz Popko (with the assistance of Ines Köhler for the period until the Old Kingdom). Of course many of these dates are only approximate. That they look so precise is the result of their purely pragmatic function, i.e. to create a list of pharaohs. Originally, they were never meant to be shown, and certainly not to be presented as a new chronological model.

For late pharaonic Egypt, our information are the chronological tables of Pestman in his P. Tsenhor. This is a purely pragmatic decision, and we realize that certainly before the advent of the 26th dynasty, the dates are approximate at best. We are considering adopting the reconstruction of TLA/AKU instead, but as this would involve changing the dates for many abnormal hieratic texts, we have so far refrained from doing so.

The Ptolemaic regnal years are based of “Theodore C. Skeat, The Reigns of the Ptolemies, München 1969”. This information was updated on the basis of “M. Depauw et al., Chronological Survey of Demotic and Abnormal Hieratic Sources, Version 1.0 February 2007, Köln and Leuven 2008” and the chronological details examined by the late Chris Bennet on his website.

The reigns of the Roman emperors are based mostly on: “P.W. Pestman, Chronologie égyptienne d’après les textes démotiques, Leiden, 1967” and “R.S. Bagnall and K.A. Worp, Chronological Systems in Byzantine Egypt, Leiden, 2004” for late antiquity.


Egyptian era years start from Thot 1.

The Diocletian era or Era of the Martyrs was in use from the fourth century AD onwards. Year 1 is AD 284, the first regnal year of Diocletian. The continuation of Diocletian’s regnal years after his death offered a solution to the confusion created by tetrarchy for the count of regnal years. The era is used for dating especially in Arsinoites and Herakleopolites. The era was later renamed ‘the era of the martyrs’ by Christians.

The Oxyrhynchos era (coming soon) was used only in Oxyrhynchus and contains two year numbers: X/X-31. The first number is a continuation of the regnal years of Constantius II, the second number a continuation of the regnal years of Julian.

NOTE: In the mid-fourth century (337-350s), papyri from Oxyrhynchus temporary use an era continuing the regnal years of Constantine I. To convert such a date, fill out only year 1.


The Egyptian indiction normally started in the beginning of the harvest (1 Pachon = 26 April), when the praedelegatio (preliminary tax rates) was issued.

There are many exceptions to this rule:

Look for a Thoth indiction, if you are dealing with:

For more information see R.S. Bagnall and K.A. Worp, Chronological Systems of Byzantine Egypt, 2nd edition (Leiden and Boston 2004).

Consular dates (30 BC and after)

Our information is based on A. Degrassi, I fasti consolari dell’impero romano dal 30 avanti Cristo al 613 dopo Cristo, Roma 1952, and R.S. Bagnall, A. Cameron, S.R. Schwartz and K.A. Worp, Consuls of the Later Roman Empire, Atlanta 1987.

New moon dates (400 BC - AD 1000)

Our information is based on the calculations of Fred Espenak, available online on AstroPixels.com. The tables are in Universal Time there, and we have added 2 hours 2 minutes for Alexandria.