BMCR 2009.05.57: Halfond on Mosshammer, The Easter Computus and the Origins of the Christian Era. Oxford Early Christian Studies

Alden A. Mosshammer, The Easter Computus and the Origins of the
Christian Era. Oxford Early Christian Studies.  Oxford/New York:
Oxford University Press, 2008.  Pp. xi, 474.  ISBN 9780199543120.
$130.00.

Reviewed by Gregory Halfond, Framingham State College
([email protected])
Word count:  1446 words
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It has been nearly ten years since a computer glitch dubbed Y2K by the
media raised millennial fears (and hackles) throughout much of the
developed world. While talking heads debated the severity of the
problem and the possibilities of an apocalyptic crash of the world's
computer systems, others raised the question whether, strictly
speaking, the year AD 2000 marked the beginning of a new millennium, or
whether that distinction belonged to 2001. As Alden Mosshammer observes
in his new monograph, The Easter Computus and the Origins of the
Christian Era, this debate caused a remarkable amount of attention to
be directed towards Dionysius Exiguus, the sixth-century putative
inventor of Anno Domini dating. Skeptics of the apocalyptic
implications of a new millennium noted that Dionysius' dating of the
nativity was quite likely wrong. They were by no means the first. The
Venerable Bede had observed back in the early eighth century that
Dionysius' dating of Christ's birth contradicted biblical, annalistic,
and patristic evidence, which favored the years BC 2/3. Most modern
scholars thus have assumed that Dionysius willfully broke with
tradition, and calculated his own (incorrect) nativity date.

Mosshammer effectively undermines this accusation in a lengthy, highly
technical, and meticulously-argued study, presented as a monograph not
as a handbook.[[1]] That he largely succeeds is a testament to his
clearly extensive knowledge of antique calendrical traditions.
Nevertheless, the exposition of his findings is not by any means
reader-friendly, and even has the potential to limit their diffusion.
There are too many occasions when Mosshammer's otherwise admirable
attention to detail distracts the reader from his larger argument.
Additionally, his lengthy, often multi-page, summaries of scholarly
debates belong in the footnotes, as they likely will be of interest
only to specialists. While Mosshammer's intention of allowing opposing
views to be heard is admirable and while these discussions are models
of sharp critical analysis, stylistically they confuse and interrupt
his narrative. And, while our author surely cannot be held responsible
for the complexity of his subject matter, which Mosshammer himself
acknowledges can be "highly technical and abstruse" (5), he makes no
concessions to his readers. These stylistic critiques are in no way
intended to diminish Mosshammer's accomplishment. His work is not only
an important contribution to the study of early Christian computus, it
also clarifies Dionysius Exiguus' role in the definition of the
chronological periodization scheme that defines our own time in
relation to antiquity. However, it is a legitimate concern that such
contributions will go underappreciated by readers unable to penetrate
Dr. Mosshammer's difficult work.

Mosshammer divides his study into four sections: "Contexts," "The
Easter Tables of Dionysius Exiguus," "Paschal Calculations in Early
Christianity," and "The Origin of the Christian Era." Part I provides a
necessary, albeit difficult, introduction to the chronological systems
of antiquity, including Olympiads, Diocletian dating, regnal years, and
indictions. Mosshammer additionally provides a brief, but helpful,
discussion of the calendrical origins of Easter, whose intimate
relationship with the Passover feast -- celebrated by the sacrifice of
the paschal lamb on the fourteenth day of the lunar month of Nisan--
made it necessary to graft a lunar-based feast onto a solar calendar.
Today, Easter falls on the first Sunday after the first full moon
occurring on or after the vernal equinox (25 March in the Roman
calendar), but standardization of observance was lacking in the
centuries prior to the Council of Nicaea (325), which formulated this
rule. Sunday observance, as Mosshammer shows, was by no means
requisite: worshipers in Asia Minor, known by their critics as
Quartodecimans, observed Pascha as a commemoration of Christ's passion
on the fourteenth day of the month, the date of the lamb's sacrifice.
Mosshammer convincingly argues that the attendees of Nicaea "apparently
or implicitly endorsed the rule of the equinox, even if it published no
rule as such" (52). Although the Council did not formally adopt a
nineteen-year cycle, as Dionysius later claimed, for early Christians
such a cycle made the calculation of the date of Easter an easier task.
Ninety-five-year paschal tables, such as the one constructed by
Dionysius, could thus be calculated, as after five nineteen-year cycles
the Paschal moon returned to the table's launch-date.

In Part II, Mosshammer examines in detail Dionysius and his table,
which Dionysius completed in AD 525. Dionysius addressed his Easter
table to a certain Bishop Petronius, who had requested the table with
the ninety-five-year table of Cyril of Alexandria nearing its end.
Dionysius claimed that his use of Anno Domini dating was his sole
innovation; otherwise he followed Cyril's cycle. Dionysius' table, like
its predecessor, consisted of five nineteen-year cycles, beginning with
the last nineteen-year cycle of Cyril. To his table, Dionysius appended
argumenta, nine or ten mathematical formulae, including formulae for
calculating the Anno Domini from the indiction. Following Charles W.
Jones, Mosshammer makes the important point that regardless of whether
the Roman Church requested the table's construction, it had no official
standing in the Western Church (61).

In Part III, the longest and most wide-ranging section of his study,
Mosshammer examines the context and (primarily eastern) models for
Dionysius' table, and the extent to which he was more follower than
innovator. Mosshammer begins by tracing the use of epacts, i.e. the age
of the moon measured in days, in Easter calculations. Mosshammer
credits Demetrius of Alexandria (AD 189-232) with first employing
epacts for the purpose of paschal calculations, basing his conclusion
primarily on later Coptic (and derivative Ethiopian) sources, which he
acknowledges have their problems (112). Epacts allowed Demetrius to
construct an Easter table based on an eight-year cycle. The oldest
surviving table, a sixteen-year chart credited to Hippolytus of Rome
(third century), while adapted to Roman customs, is based on this
Alexandrian eight-year cycle. It was the third-century polymath,
Anatolius of Laodicea, who introduced the nineteen-year cycle with the
new moon on 22 March and an equinoctial date of 21 March (25 Phamenoth
in the Egyptian calendar). According to Anatolius' methodology, Easter
could fall no earlier than the fifteenth day of the moon. Over the
course of the fourth-century, as Mosshammer shows, Anatolius' work
served as a model for subsequent Alexandrian tables, augmented by the
employment of Diocletian dating, which "arose in response to the
introduction of the consular year and the loss of Egypt's special
status as a royal domain" (177). Around the early fifth-century,
Annianus of Alexandria introduced the 532-year period to Easter
calculation. In his Pachoualion, he calculated a new base date for
Creation (Sunday, 25 March, 5492), and adjusted Anatolius' epact so as
to coordinate the cycle with the Alexandrian civil year. Annianus' work
provided much of the theoretical basis for Cyril of Alexandria's
paschal list, which commenced in the year AD 399.

In Part IV, Mosshammer turns to the central question of the origins of
Dionysius' Christian era. His principal argument in this section is
that Dionysius was not the originator of his infamous nativity dating.
Mosshammer observes that Pandorus, a contemporary of Annianus, had used
a similar chronology. Pandorus had rejected Annianus' calculation that
the Passion had taken place in the nineteenth year of Tiberius and the
Resurrection in the twentieth, and dated both events to the nineteenth
year. Pandorus, Mosshammer argues, was following Julius Africanus (late
second-early third century), who dated the Resurrection to 25 March, AD
31. Africanus' dating implies a Nativity date of 25 March, 1 BC (cosmic
era 5501). Pandorus, Mosshammer argues, probably was not Dionysius'
direct source, just as he was not the ultimate source for this
chronological scheme. Pandorus was merely "reasserting" the dating of
Julius Africanus against Annianus (421). Anatolius too borrowed from
Julius Africanus in composing his nineteen-year cycle, and Julius'
Christian era was implicit in his table. Despite his reliance on the
work of Annianus, Cyril of Alexandria did not adopt the latter's
Christian era, but rather preferred the 'traditional' Alexandrian
nativity date. Cyril's table, of course, served as the foundation for
that of Dionysius. Thus, Mosshammer concludes, "The Christian era of
Dionysius is no more than the cosmic year 5501 in the system of Julius
Africanus, adapted first to the Alexandrian civil year, then to the
Roman [civil] or indictional year" (435).

Although the history of Christian computus certainly does not end with
Dionysius, Mosshammer concludes his study with the sixth-century monk,
leaving aside the fascinating question of the transmission of
Dionysius' table and his Anno Domini dating in subsequent
centuries.[[2]] However, Mosshammer's contribution to our understanding
of Christian chronology is a significant one, clarifying the extent to
which the system that Dionysius introduced to the West was of eastern
origin, and its adoption into a Roman context. In doing so, Mosshammer
redeems the much-maligned Dionysius from the charges of his critics,
both medieval and modern.

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Notes:


1.   For students, a fine introduction is Arno Borst, The Ordering of
Time, trans. Andrew Winnard (Chicago: University of Chicago Press,
1993). Briefer, but slightly more technical, is the introduction by
Faith Wallis to her translation of Bede, The Reckoning of Time,
(Liverpool: Liverpool University Press, 1999), xxxiv-lxiii.

2.   A problem discussed by Charles W. Jones, "The Victorian and
Dionysiac Paschal Tables in the West," Speculum 9 (1934), 408-421;
Charles W. Jones, "Two Easter Tables," Speculum 12 (1938), 204-205.