1.1.1. Dormition on August 7 and opening of the “Latrocinium” of Ephesus on August 8
Peter the Iberian starts his liturgical services as a bishop on the day of a great feast that is, according to van Esbroeck, Dormition. However, its date is August 7, and not August 9 that we know as an early date of Dormition. Thus, van Esbroeck goes into long speculations based on a hypothetical use of the calendar of the Book of Jubilees in Jerusalem during the anti-Chalcedonian patriarch Theodosius (451—453). This is, I think, not a good idea, because all the known Christian 364-day calendars have different structures than the old calendar of the Jubilees. What is the worst, van Esbroeck arrives, even with these speculations, to reconciliation of the date August 7 with the date August 8, but not 9: “...August 7th in Peter’s Life is really August 8. Since Peter celebrates at sunset on the 8th, he is already celebrating the Assumption of the Virgin on the 9th.”  However, beginning of the day at evening and not at morning would contradict to van Esbroeck’s “sacerdotal calendar,” where day starts at morning. This reconstruction looks as neither precise nor consistent. Fortunately, it is superfluous.
In the 450s, only the earliest recension of the Transitus story was available (e. g., such as preserved in the Ethiopic Liber Requiei, CANT 154) where the Dormition and Assumption cycle is shaped as a triduum: annunciation from the Angel (first day), gathering of apostles (second day), Dormition, deposition, and Assumption (third day). In the Ethiopian rite, this cycle is still partially preserved, while not reflected in the Ethiopian Synaxarium, already influenced by the later Coptic rite. In the Ethiopian hymnary, Deggwa, before the Assumption feast on August 9 (Naḥasē 16), there is, on August 8 (Naḥasē 15), a feast of “Gathering” (Gubbace) that means gathering of apostles in Sion before the deathbed of Theotokos. The same feast was also preserved in the medieval recension of the Georgian rite, while with an appropriate shift of dates (August 13, because of the different organisation of the whole cycle). Thus, the earliest Dormition triduum was placed on the days from August 7 to August 9, because the gathering of apostles (August 8) is the second day of the earliest triduum, not the first. The date of the “great feast” on August 7 in the Life of Peter the Iberian is the first day of Dormition celebrated according to the Transitus tradition as it is in the Liber Requiei.
The appearance of this liturgical cycle can be dated. The 449 Council of Ephesus (subsequently called Latrocinium in Rome) broke the trend (not always strict but quite clear) established by the three previous Ecumenical Councils to match the opening with the Pentecost. Instead, the Council of Ephesus was opened on August 8. The purpose of the council was to defend Theotokos, and so, this date is hardly explicable otherwise than within the triduum from 7 to 9 of August, where August 8 corresponds exactly to gathering of apostles.
This date has had nothing to do with the local tradition of Theotokos cult in Ephesus (where we know the date of Dormition May 23), but the council of Ephesus was gathered not by the local clergy but by Emperor Theodosius. However, the Emperor together with his sister Pulcheria and his wife Eudocia were preoccupied in establishing another Theotokos cult, located in Palestine and connected to Constantinople and not to Ephesus. This was the time when a new family of Transition accounts emerges, “Bethlehem and Incenses,” whose main representative is the Syriac “Dormition in Six Books” (CANT 123, 140, 150). It starts with a preface explaining how the truth about Dormition in Palestine and deposition in Gethsemane was brought from Ephesus, where the Transitus account has been preserved in secret by the heirs of John Theologian. It is clearly an attempt to create an alternative to the local Ephesian tradition that Theotokos died in Ephesus and was buried by John Theologian, according to her will, in an unknown place (with no assumption at all).
The establishment of the earliest form of Dormition cycle in Palestine (7 to 9 August) is datable to 440s, after 438 (first solemn visit of Eudocia to Jerusalem) and before 449 (Council of Ephesus).
 Life of Peter the Iberian, § 79: “Yet once he had arrived at the holy Church of Maiuma, being carried about by all, he sat on the throne on the seventh of the month of Ab [= August], when there took place a great, holy, and heavenly feast ( ܥܐܕܐ ܪܒܐ ܘܩܕܝܫܐ ܘܫܡ̇ܝܢܐ) and life for the souls of each of them” (Horn, Phenix Jr, John Rufus…, 118/119).
 van Esbroeck 1993, 223–225.
 B. Lourié, Les quatre jours « de l’intervalle » : une modification néotestamentaire et chrétienne du calendrier de 364 jours, in: M. Petit, B. Lourié, A. Orlov (éds.), Église des deux Alliances : Mémorial Annie Jaubert (1912—1980) (Piscataway, NJ, 2008) (Orientalia Judaica Christiana, 1) 103–133; idem, Calendrical Implications in the Epistle to the Hebrews: Seven questions concerning the liturgy of the Sabbath rest, Revue biblique 115 (2008) 245–265; idem, Calendrical Elements in 2Enoch, in: G. Boccaccini, A. Orlov (eds.), Proceedings of the Fifth Enoch Seminar, Naples, 2009 (forthcoming).
 van Esbroeck 1993, 223; van Esbroeck supposed that the date of Assumption in the Coptic rite, August 9 (Mesore 16) is the earliest and genuine date of Dormition.
 For the chronology of the earliest Transitus, see now Shoemaker, The Ancient Traditions of the Virgin Mary’s Dormition and Assumption; for different types of the early Dormition cycles (triduum or more complicated), see Lourié 2007.
 P. Jeffery, The Liturgical Year in the Ethiopian Deggwa (Chantbook), in: E. Carr (ed.), ΕΥΛΟΓΗΜΑ: Studies in Honor of Robert Taft, S.J. (Rome, 1993) (Studia Anselmiana, 110) 199–234, here 233. Jeffery’s reference to Budge’s translation of the Ethiopian Synaxarium is here misleading. In fact, not only Budge’s translation but even the whole manuscript evidence used for the critical edition say nothing about Dormition/Assumption on Naḥasē 15 (Julian August, 8); cf. I. Guidi, S. Grébaut, Le Synaxaire éthiopien. Mois de Nahasè et de Pâguemèn (Paris, 1913) (PO 9,4) 325–335.
 M. van Esbroeck, Ein georgischer liturgischer Kanon für Maria Himmelfahrt, in: R. Schulz, M. Görg (hrsg.), Lingua restituta orientalis. Festgabe für Julius Assfalg (Wiesbaden, 1990) (Ägypten und Altes Testament, 20) 89–110 [French tr.: idem, Aux origines de la Dormition de la Vierge. Études historiques sur les traditions orientales (Aldershot, 1995) (Variorum Reprints. Collected Studies Series CS 380) ch. XIV].
 See, on all this, Lourié 2007.