Biblical Studies, Church History

Religious Calendars in Antiquity Some Background to the Orthodox Church of Ukraine’s Recent Calendar Switch

Published on: September 13, 2023
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Religious Calendars
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On September 1st, the Orthodox Church of Ukraine moved to the Revised Julian (“New”) Calendar. Fixed festivals will now align with Gregorian Calendar dates. In a statement, the OCU Synod stated that the Julian (“Old”) Calendar had become associated predominately with the Russian tradition. In addition, they point out that the Julian system has no special sacred significance and was originally adopted due to its use as the Roman civil calendar. While political motivations underlie this decision, religious calendars have long been influenced by political considerations and have frequently conformed to the civil one. In this piece, I will survey some of this history from ancient Israel and Judah through the Byzantine period while avoiding rehashing debates of “Old” vs “New” calendars.

While the first command God gives to the people of Israel as a collective pertains to the establishment of a distinct calendar (Exod 12:2), scripture gives no specifics. It is even possible that different texts reflect distinct calendrical systems. In fact, we find three different naming conventions for the months in biblical texts. The earliest writings possibly adapt Canaanite names associated with agricultural seasons (e.g., “Abib” Exod 13:4 and “Ziv” in 1 Kings 6:1), as is also attested in the 10th century Gezer calendar. Other texts use ordinal numbers (e.g., “First” in Gen 8:13 and “Second” in Exod 16:1). Postexilic works employ Babylonian names (e.g., “Nisan” in Neh 2:1 and “Adar” in Ezra 6:15). While potentially differing in particulars, it is generally assumed that all these systems represent some form of 354-day lunar calendar (12 x months of varying length), as was common among their neighbors.

However, other evidence points to the potential use of a schematic 360-day calendar (12 x 30 days), which was common in Mesopotamia and Egypt. Such a calendar provided a fixed system for administration and accounting unencumbered by the unpredictability of astronomical observation. A number of portable calendars discovered from Iron Age Judah suggest its use, while possible textual corroboration is provided by several works in the Hebrew Bible (e.g., Priestly literature).

During the 2nd millennium BCE, Babylon developed a distinct lunar calendar, which became the official calendar of the Assyrian, Babylonian, and Persian Empires. Under Persian rule in particular, this calendar was disseminated widely. It is at this time that the Jewish people adopted it, including month names, new moon prediction methods, and fixed intercalation cycles. Some scholars argue that a Spring start of the year is also embraced at this point. So prevalent was this system that Jews as far away as Elephantine in Egypt use it alongside the local Egyptian civil calendar. While the Seleucids retain the Babylonian calendar, the new year shifts to the Fall and a new era system, beginning with the start of Seleucid rule, is implemented. Even in the medieval period, many Jewish texts still employ this same system.

With the wane of Seleucid domination in the 2nd century BCE a shared calendar in the Levant ceases. Local populations adopt distinct systems to assert their unique identities. Under Hasmonean rule a local Judean calendar likely first emerges. While maintaining many features of the Babylonian system, it asserts local control of intercalations and sighting new moons while coordinating festivals according to the Jerusalem cult. It is in this period that calendrical debates arise between 354-day and 364-day systems. The 364-day calendar (12 x 30 days [31 days for 1 month each season]) is a purely schematic system able to be divided evenly into 52 weeks of 7 days. The priestly septenary focus seeks to fix festivals on the same day every year to avoid sabbath conflicts. While we see evidence of it in the Astronomical Book and Jubilees, it becomes a defining characteristic of the later Qumran community in its opposition to the central Jerusalem cult.   

With the arrival of Rome comes the spread of its solar calendar as the official civil one. Julius Caesar had recently reformed the older Republican calendar in 46 BCE to be more in line with the Egyptian civil system (12 x 30 days + 5 extra days). This “Julian” calendar supplanted local ones except for many parts of the east (e.g., Egypt, Asia Minor, and the Levant) where they persisted alongside. Christians began coordinating festivals according to this calendar, while Pascha continued to be reckoned based on the lunar cycles but in relation to the Julian equinox.

By this time, the Roman new year was being observed in January. However, many provinces began the year at different times. For example, Augustus’s birthday on September 23 is attested in inscriptions across the province of Asia as one alternative. By the 4th century, the indiction tax assessment marks the beginning of the Byzantine civil year. Initially, it is placed on September 23rd since it likely began around Asia Minor where this date already began the year. However, it moves to September 1st likely in the 5th century. In some of the earliest Byzantine liturgical calendars, the conception of John the Baptist on September 23rd marks the new year. Although this feast serves a logical start to the church year, later calendars become adjusted to the new indictional year.

Elsewhere, liturgical calendars conformed to local civil ones. For example, Egyptian Christians aligned their festivals with the Alexandrian calendar. We find papyrus evidence that indicates that indictions in Egypt were tied early on to the start of the Egyptian civil year, which began on Thoth 1 (= August 29). This date still serves as the start of the year in the Coptic Calendar today.  

The history of the religious calendar is complex. While a correspondence between civil and religious calendars indicates a willingness to integrate with the larger society—especially when the religion is shared—Jewish and Christian calendars became less open to revisions based on the civil system over time to maintain their independent minority identities as they came under rulers with different religions. In the case of the Byzantine tradition, this continued until the 20th century when many churches finally adopted the Gregorian calendar—a relatively minor calendrical update compared to ancient ones. Ukraine thus represents a desire not only to mark themselves as distinct from a tradition of which they were long a part but also to integrate further with both the wider Orthodox world and modern civil society.

For Further Reading:

Ben-Dov, Jonathan. “A 360-Day Administrative Year in Ancient Israel: Judahite Portable Calendars and the Flood Account.” Harvard Theological Review 114, no. 4 (2021): 431–50.

Ben-Dov, Jonathan. Head of All Years: Astronomy and Calendars at Qumran in Their Ancient Context. Leiden: Brill, 2008.

Mosshammer, Alden A. The Easter Computus and the Origins of the Christian Era. Oxford: Oxford University Press, 2008.

Stackert, Jeffrey. “The Priestly Sabbath and the Calendar: Between Literature and Material Culture.” In Contextualizing Jewish Temples, edited by Tova Ganzel and Shalom E. Holtz, 49–64. Leiden: Brill, 2021.

Stern, Sacha. Calendars in Antiquity: Empires, States, and Societies. Oxford: Oxford University Press, 2012.

Stern, Sacha. Calendar and Community: A History of the Jewish Calendar, Second Century BCE–Tenth Century CE. Oxford: Oxford University Press, 2001.

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About author

  • Richard Zaleski

    Richard Zaleski

    Teaching Fellow at the University of Chicago

    Richard Zaleski holds a PhD in New Testament and Early Christian Literature from the University of Chicago Divinity School. He is currently a Teaching Fellow at the University of Chicago. He focuses his research on the biblical text and its reception in early Judaism and Christianity.

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Public Orthodoxy seeks to promote conversation by providing a forum for diverse perspectives on contemporary issues related to Orthodox Christianity. The positions expressed in the articles on this website are solely the author’s and do not necessarily represent the views of the editors or the Orthodox Christian Studies Center.


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