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A Scientific Examination of the Orthodox Church Calendar

Ch. 4: The Essence of the Church Calendar

by Hieromonk Cassian

God exercised His authority over time through the Holy Fathers at the Œcumenical Synods. 24 This is vividly expressed by Synodal decrees, wherein the words of Holy Scripture are pronounced: "It seemed good to the Holy Spirit, and to us." 25 Although the calendar is a human invention, its definitive acceptance by the Holy Orthodox Church elevates its status to the Divine. Therefore, the violation of the calendar is a sin, and according to the ordinances of the Œcumenical Synods, it is a sin against the Holy Spirit, Who inspired these Synods. Furthermore, following the words of the Holy Gospel of Saint Luke, "And whosoever shall speak a word against the Son of Man, it shall be forgiven him: but unto him that blasphemeth against the Holy Spirit it shall not be forgiven," 26 logic dictates that this is the gravest of sins.

Strictly speaking, the Julian Calendar is not a Christian calendar; it is actually a pagan one. When Julius Caesar inaugurated his eponymous calendar in 46 b.c., it was intended for general civil use in the Roman Empire, and so it remained until the First Œcumenical Synod (Figure 4). Summoned in Nicaea, a town of Asia Minor, the week before the Feast of Pentecost in 325, this celebrated Synod not only defended some of the most important dogmatic principles of Christianity, but also appropriated the Julian Calendar for ecclesiastical use by conjoining it to the Jewish Calendar in the establishment of a uniform calculation of Pascha—the Paschalion—, a calculation that was to supersede the various local practices which up to that time had caused liturgical confusion within the Church. It did so by introducing a universal time-reckoning scheme, the Great Indiction, or Cycle from the Creation of the World, 27 which remains to this day as the basis of all of the service books of the Orthodox Church. The Divine Services, immutably determined by the Church Calendar, consist of two concurrent cycles: the immovable cycle of Feasts, those which are fixed to a specific calendar date, and the movable cycle of Feasts, those which are dependent on the Feast of the Resurrection, the date  of which is variable. (After the calendar reform, all Feasts became movable, as will be shown later in the chapter, "Liturgical Havoc Wreaked by the 'New Julian' Calendar.") Thus, when speaking of the Church Calendar, we mean both the immovable, Menaion (from the Greek "men," "month") cycle and the movable, Paschal cycle as well.

The essential role of the Julian Calendar in the Divine Services lies in its relationship to the first cycle, that of the immovable Feasts. The Julian Calendar serves as a framework for the Menaion cycle; yet, the two are not coterminous. The Menaion cycle differs from the Julian Calendar, inasmuch as it has certain characteristics modelled on Biblical precedents which distinguish it from the civil reckoning of time. For example, the liturgical or ecclesiastical day always runs from evening to evening, following the Scriptural reckoning: "And there was evening, and there was morning, the first day." 28 This is why the daily liturgical order starts with Vespers. With the Julian computation of time, however, the civil day runs from midnight to midnight. This discrepancy is not unimportant, because the difference between the liturgical and civil reckoning will be an entire day for events between dusk and midnight. Likewise, there is an analogous discrepancy with the reckoning of annual events: the ecclesiastical year (i.e., the Indiction) begins on September 1, while the civil year begins on January 1. Therefore, there will be a difference of one year between the ecclesiastical and civil reckonings for events between September 1 and December 31. In addition, the liturgical hours are designated differently than the civil hours of the Julian Calendar: the First Hour corresponds to 7:00 a.m., the Third Hour to 9:00 a.m., and so on. Hence, the Menaion (in Slavonic, "Mesetsoslov" ) 29 is a liturgical book which details the cycle of ecclesiastical celebrations for the Faithful, while the Julian Calendar reckons time periods in general and is for use outside of the Church.

Distinct from this immovable cycle of Feasts is the Paschal cycle, which derives from and is linked to the ancient Jewish Calendar. This linkage is a result of Christ's Passion having been directly connected to the Jewish Passover; strictly maintaining the sequence of events described in the Holy Gospel, the Orthodox Church always celebrates the Resurrection of Christ after the Passover. From antiquity, the chosen people of the Jews celebrated the Passover in accordance with its lunar calendar, 30 a practice faithfully observed by the Lord Jesus Christ. The Word of God incarnate was a Jew, Who obeyed the requirements of the Old Testament, because He did not come to destroy the Law, but to fulfill it. 31 As the God-Man, Christ fulfilled what was lacking in the Law by offering Himself as a Sacrifice for the redemption of mankind from sin, death, and damnation, becoming thereby a New Passover—"the Sun of righteousness" 32 —for all who believe in Him. Thus, the Old Testament Pascha, 33 on which the Jews commemorated their Exodus from Egypt, was replaced by the New Testament Pascha, on which Christians celebrate the deliverance of their souls from slavery to the noetic Egypt, that is, sin. 34 Saint John Chrysostomos draws a theological parallel between the Old and New Testament Passovers:

The Jewish Passover was a foreshadowing, while the Christian one is truth.... The former was a deliverance from corporeal death, while the latter brought an end to the wrath of God, under which the whole universe had fallen; the former was a deliverance from the Egypt of old, the latter was a ransom from idolatry; the former did away with Pharaoh, the latter with the Devil; after the former, the Promised Land followed, while after the latter, Heaven. 35

The Church Calendar is thus a combination of two harmoniously interwoven cycles, the Menaion cycle, which utilizes the solar Julian Calendar, and the Paschal cycle, which relies on the lunar Jewish Calendar, and it is only under these names that the Church Calendar is encountered in service books. The fruit of the ingenious efforts of numberless scholars and theologians, the Church Calendar alone fulfills the canonical and dogmatic requirements of the Orthodox Faith. All other calendars are unable to fulfill these requirements practically, because the combination of the movable and immovable cycles is univocal and unique. The Church Calendar is inseparable from the cycles of the sun and the moon, in much the same way that a replica of a picture is inseparable from its original: without the original, the replica would not exist, and in the same way, the Church Calendar reflects the solar and lunar cycles. Therefore, every effort to replace the Church Calendar is doomed to failure, for the Church Calendar is, by definition, never at odds with the Biblical, canonical, and liturgical dictates of ecclesiastical life. But let us prove this.

In the immediate centuries after Christ, Christianity quickly spread throughout the Empire (and beyond). The impediments to communication at the time, however, allowed local traditions to develop an undue strength. So it was that the early Christians did not necessarily celebrate Pascha at the same time. It thus became imperative to formalize the Apostolic teaching concerning the celebration of this Feast of Feasts as an inviolable rule. The Seventh Apostolic Canon proclaims: "A Bishop, a Presbyter, or a Deacon who celebrates the Holy Day of Pascha before the vernal equinox, together with the Jews, shall be deposed from his sacred rank." This strict rule is the fundamental criterion of the Christian Paschalion. It stipulates that Pascha be celebrated after the Jewish Passover 36 and after the vernal equinox. The Passover is always celebrated on the fourteenth of Nisan (March/April), which is the date of the first full moon of spring in the Jewish Calendar. Therefore, the Paschal full moon is determined by the lunar calendar, while the vernal equinox is determined by the solar calendar. The Nicene Paschalists faced the problem of how to combine the lunar and solar calendars in compliance with the requirements of the Seventh Apostolic Canon. Their primary objective was to link permanently, both in theory and in practice, the cycle of the moon with the cycle of the sun, thereby obtaining an indivisible and harmonic bond between the two differently-based calendars. This would preserve the sequence of events in the last days of our Lord Jesus Christ as they are described in the Holy Gospel.

In order to appreciate the ingenuity of the Church Calendar, it is necessary to evaluate it from the perspective of the Nicene Fathers. We must consider their explicit goal in composing a Christian calendar, the problems they faced in undertaking this task, and the manner in which they tackled these problems. For the Synod of Nicaea, the overriding concern was how to fulfill canonical requirements in the composition of the Paschalion. Its goal, therefore, was to harmonize the rhythms of the lunar and solar cycles exactly. This type of exactitude is quite different from that which the Gregorian reformers sought. Unlike the Holy Fathers of Nicaea, the latter set as their goal the attainment of an "astronomically accurate" calendar, as stated in the Papal bull "Inter Gravissimas." 37 As we shall see later, the concept of "astronomical accuracy" is wholly relative and extremely uncertain. Contemporary science readily admits that the composition of a calendar which is "astronomically accurate" in relation to the reckoning of fictive time, such as the Gregorian Calendar, is unfeasible. Thus, the Gregorian reformers ultimately failed to achieve their goal, whereas the Nicene Fathers entirely succeeded in achieving theirs, which was again, a different one. Let us now consider how.

In order to synchronize the two differently-based calendars—viz., the Julian Calendar, which is solar, and the Jewish Calendar, which is lunar—, it is necessary to determine a period of time after which the dates of each calendar will "realign." For example, let us say that a cycle begins with the day on which March 1 ( Julian Calendar) occurs simultaneously as Nisan 1 ( Jewish Calendar). This cycle will be considered complete when March 1 and Nisan 1 fall once again on the same day. We have already discussed the nineteen-year cycle ascribed to Meton of Athens—a cycle which several ancient civilizations, Eastern and Western (Babylon, Greece, China, et al.), had discovered independently in the middle of the first millennium b.c. The chief merit of the Metonic cycle resides in its determination of the least common multiple of the lunar and solar cycles. Again, as explained earlier, in the Metonic cycle, the lunar year has 354 days, while the solar year has 365 days. The addition of seven embolismic months, each having thirty days, "realigns" the lunar and solar years after a period of nineteen years. This lunisolar harmonization appealed to the Nicene Fathers, because they needed just this sort of link between the lunar phases and the vernal equinox, in order to conform to the dictates of the Seventh Apostolic Canon. However, for their purposes, the Metonic cycle had a slight drawback: it was designed for a solar year of 365 days, whereas the Holy Fathers intended to use the Julian Calendar with its solar year of 365.25 days. When the Metonic cycle is applied to the Julian Calendar, the extra six hours of the Julian solar year add up to four days and eighteen hours over the course of nineteen years.

Thus, the First Œcumenical Synod faced a quandary. If, in a given year, Nisan 1 coincided with March 1, after nineteen years, Nisan 1 would apparently begin six hours earlier than March 1, though the actual difference between the two dates would be four days and eighteen hours. Here, again, the least common multiple of this difference had to be found. This was easy enough: after four nineteen-year cycles (i.e., seventy-six years), the apparent difference of six hours quadruples, adding up to an entire day. In reality, however, the actual difference of four days and eighteen hours also quadruples, meaning that the vernal equinox occurs nineteen days later, i.e., at its original starting point—and thus a full cycle is completed. These simple calculations were carried out in 330 b.c. by the Greek astronomer Callippus, who discovered an astounding natural phenomenon: Thus, by quadrupling the Metonic cycle—a Callipic cycle—, the Jewish lunar year is synchronized to the Julian solar year. Although the Julian Calendar has some imprecision, this imprecision is found to almost the same extent in the Jewish Calendar. Thus, the vernal equinox, which moves ahead by the Julian calculation, moves ahead according to the Jewish one as well.

The Callipic cycle, therefore, made it possible to calibrate the Metonic cycle to the Julian solar year. But in order to make this adjustment work properly, it was imperative to know the average lengths of the lunar month and of the solar year. 38 It is unreasonable to assume, as some modern scholars do, that the Nicene Fathers were ignorant of the accurate measurements of these intervals, for these measurements were already known from very ancient times. For example, by the middle of the third millennium b.c. in Babylon, and by 104 b.c. in China, the precision of their determination nearly matched the accuracy of contemporary scientific methods. Furthermore, considering the computations of the American astronomer Simon Newcomb (1835-1909) in regard to the change in the day during the millennia, the correspondence between ancient and contemporary data is astounding; we can only guess what astronomical means were used by the ancients to accomplish such precision. In any event, for the purposes of Christian chronology, the Holy Fathers of Nicaea accepted the length of the lunar month to be approximately 29.53 days and the length of the solar year to be 365.25 days. (Later, we will elucidate how the exactitude of these figures is often deemed satisfactory, even for the most up-to-date astronomical research.)

These figures are crucial to the formation of the Great Indiction, the aim of which is, as we have shown, the combination of the solar cycle with the lunar one. We have already discussed the fact that after a period of nineteen years, new and full moons fall on the same dates as they initially did. Analogously, after a period of twenty-eight years, the sun completes a cycle in which the calendar dates fall once again on the exact same days of the week as they did at the beginning of this cycle. Thus, the Great Indiction, a period of 532 years, is established by joining the nineteen-year lunar cycle with the twenty-eight-year solar cycle—in the language of arithmetic: 19x28=532. In other words, the Great Indiction can be considered either as nineteen twenty-eight-year solar cycles or as twenty-eight nineteen-year lunar cycles. 39 This, then, is how the unique astronomical, mathematical, and Paschal rhythm of the Church Calendar was obtained. Whenever the Great Indiction elapses, the cycles of the sun and of the moon and the days of the week revert to their initial order. Since 1941, we have been in the Fifteenth Indiction; Pascha of  that year was celebrated on the same calendar date as Pascha in 1409, i.e., 532 years earlier. Likewise, Pascha in 1998, April 6 (Old Style), was celebrated on the same date as the years 402, 934, and 1466.

Nineteen Julian solar years exceed nineteen Jewish lunar years by one hour, twenty-eight minutes, and fifteen seconds. 40 This means that after the passage of nineteen solar years, the lunar phases occur again on the same dates of the month, only they do so one hour, twenty-eight minutes, and fifteen seconds earlier; and after the passage of sixteen nineteen-year cycles (i.e., 304 years), they occur almost a day earlier. 41 This is the reason that the Paschal full moon since the time of the First Œcumenical Synod has been appearing earlier and earlier, with respect to its appearance in 325. At that time, Nisan 14 coincided with the vernal equinox; now it is lagging behind the vernal equinox by about ten days. In other words, the earliest Paschal full moon at the time fell on March 21 (Old Style), while it now falls on March 18 (Old Style). Likewise, this lagging behind the vernal equinox can be observed in the Julian Calendar: in 325 it fell on March 21 (Old Style), while today it falls on March 8 (Old Style). The amazing thing is that the Nicene Paschalists succeeded in linking the two calendars—inexact in themselves—, so that ultimately they obtained a nineteen–year cycle which is of great scientific merit, one that unerringly reckons, even to this day, the lunar phases and their connection with the vernal equinox.

Moreover, when the Evangelical sequence of events between the Jewish Passover and the Christian Pascha is maintained as it is in the Nicene Paschalion, over the course of time, the Jewish and Christian feasts gradually move apart from each other, precisely because the lagging of the Julian Calendar behind the vernal equinox is slightly greater than that of the Jewish Calendar. This lagging of the Orthodox Pascha was called "an advantage" by the prominent Byzantine canonist, Hieromonk Matthew Blastares of Thessalonica ( fl . 14th cen.). His claim is the antithesis of that of contemporary ecumenists, who call this lagging "a defect." The phenomenon demonstrates the acceleration of the relative velocity of the moon in relation to the earth through the course of centuries. It is a complicated problem for scientists undertaking the compilation of an exact lunisolar calendar, which we will deal with in detail in the chapter "Science—In Support of the Church Calendar." One can only marvel at the ingenious solution of this complex astronomical problem. Furthermore, the drawing apart of the Jewish Passover from the Orthodox Pascha has deep theological significance, clearly indicating the proportionally increasing hostility over the centuries of Judaism towards Christianity. This brings to mind the words of the Savior: "...For the prince of this world cometh, and hath nothing in Me." 42 By the same token, this chronological distancing of the central Orthodox Feast from the Jewish one providentially signifies the spiritual distance between these faiths, viz., that Orthodoxy has nothing in common with Judaism. For the adherents of the Gregorian Paschalion, just the opposite is the case, since they often celebrate their Easter together with, or before, the Jewish Passover.

Thus, in practice, there is an indefectible natural phenomenon, observable within the course of a human life, which serves as the basis of the Church Calendar. 43 Our aim is not to show in detail how this was accomplished, for those who desire to know this can consult the textbooks of the Orthodox Paschalion; rather, our purpose is to demonstrate that given the elementary knowledge just presented, an understanding of the Orthodox Church Calendar is quite easy. From an ecclesiastical viewpoint, a study of the Paschalion does not require astronomical details—such are not necessary to the goal of theology. It is enough to be acquainted with the structure of the Church Calendar and to grasp the synchronization of the movable and immovable cycles, readily apparent in the Typicon of the Church, which establishes the proper ordering of the Divine Services. It is unnecessary for the ordinary Priest to investigate highly technical matters, which are hardly intelligible to the average person. For an Orthodox Priest, what is essential is the ability, upon opening the service books, to apprehend the immovable Feast of the day and its relationship to the Paschal cycle, so that he can celebrate the Divine Services in accordance with the requirements of the Church Typicon. For example, in order to determine the appointed Epistle and Gospel readings for the Divine Liturgy for every day of the year, it is necessary to know how many weeks have passed since the movable Feast of Pentecost.

This conscious overlooking of the astronomical aspect of the Orthodox Paschalion is often a source of doubt in rationalistically-inclined minds. Such doubts, however, are a manifestation of an ignorance of the essence and goal of the Paschalion. The perennial tradition of the Holy Fathers has established an extremely simple, yet exact, method for the calculation of Pascha—without calendars—, one based on the most important criterion: that expressed by the Seventh Apostolic Canon. This method is so perfect in practice that even until the present, the determination of the vernal equinox, the full moon, and the Jewish Passover based on it corresponds to real events. The consistent coincidence between theory and practice achieved by the Church Calendar, from antiquity to modernity, inspires confidence that it is not the mere fruit of rationalistic human philosophizing, but is sanctified for liturgical use by God Himself, according to the words of the Holy Œcumenical Synods: "It seemed good to the Holy Spirit, and to us." 44

The fact that the Orthodox Church has released Her Faithful from an obligation to know the astronomical technicalities of the Paschalion is not a flaw; on the contrary, it is a strength. Just as schoolchildren need not reinvent letters and numbers anew, so it is for Orthodox who possess the Paschalion. Without delving into a semeiological analysis of alphanumeric figures, schoolchildren take these conventional graphic symbols for granted, once they have learned them; in the same manner, the Church Calendar, since its development and subsequent testing by the Holy Fathers, has been handed down to each new generation of Orthodox for practical, liturgical purposes. Quite simply, it is impossible to create another, similar calendar—even the smallest change would lead to a discrepancy with the cycles of the sun and the moon, and, more importantly, would allow for human infringement in the Divinely-inspired liturgical texts. This is neither permissible nor exigent. Therefore, any Orthodox who thinks that the Faith must be "corrected" proves that he does not wish to obey his Holy Mother, the Orthodox Church, but rather that he desires to "reform" Her; that is, he does not accept Her as She is, protesting instead against Her essence. Such an individual may be called a "reformer," a "Protestant," or whatever, but he may not be properly called Orthodox. An Orthodox is one who observes diligently and immutably the teachings of the Holy Orthodox Church, which long ago sanctified the externals of our Faith, releasing us from the need to "reinvent" these externals.

Orthodox Christians have much more pressing concerns than astronomy, the chief of these being the mastering of the science of spiritual life, viz., the struggle with sin and passions, both those found internally within a man and those found externally in his surrounding environment. This science of sciences directly involves one in the future, eternal life, and is infinitely more important than the present, temporal life, despite the fact that it is unfortunately neglected and forgotten today. The Holy Fathers discharged us from the onerous task of composing a liturgical calendar and accompanying services, so that by utilizing what they have passed on to us, by way of Holy Tradition, we might be able to pursue the universally essential fight for salvation unencumbered by technical distractions. With the eternal salvation of the human soul as the focal point, the imaginary problem of "meticulosity" posed by the Gregorian calendar reformers not only pales, but literally vanishes, as a consideration, in the same way that in mathematics every finite number in relation to infinity is equal to zero. Therefore, even if the "concern" of the Gregorian Paschalists were well grounded, if it displaces our most important concern and objective—salvation—, it becomes groundless and senseless. What need is there to "reinvent" that which has already been established once and for all times?

The natural phenomenon which forms the basis of the Orthodox Church Calendar impressed the brilliant German mathematician and astronomer, Carl Friedrich Gauss (1777-1855 ), so much that he constructed his own "Paschalion," reproduced herein as Addendum 2, "The Gaussian Formula for the Orthodox Calculation of Pascha." As far as modern science is concerned, Gauss' method is purely classical physics. However, the theory of relativity, first introduced in the realm of physics, revolutionized our thinking by its discovery that there are no constant phenomena in nature. Yet it is wondrous to observe how the orderly Paschal theory of Orthodoxy stands up to all such new discoveries, and, furthermore, not only does not contradict them, but just the opposite, serves as the basis for the most modern astrophysical and chronometrical measurements. Perhaps this proves that genuine science merely rediscovers Biblical truths and should thus be guided by them.


23. Resurrectional Canon to the Most Holy Theotokos, Tone 2, Ode 3, Troparion 1.

24. An Œcumenical Synod is a convocation of Bishops from all of the local Churches for the resolution of matters concerning the Church as a whole (T. Koev, Orthodox Catechism and the Epistle of the Eastern Patriarchs on the Orthodox Faith [Sofia: Texim Ltd., 1991], p. 34 ).

25. Acts 15:28.

26. St. Luke 12:10.

27. The starting point of the Great Indiction is Sunday, September 1, 5508 b.c.

28. Genesis 1:5.

29. "Menaion" is used as a collective name for the Menaia, the twelve volumes corresponding to the months of the year, in which the Feasts of the immovable cycle are set forth.

30. [The ancient Jewish Calendar was the product of the spiritual and scientific insight of Saint Moses the God-seer (   ca. 1430 b.c.). This Holy Prophet lived for 120 years: his first forty years he spent as a prince at the court of Pharaoh, where he received the best education available, including studies in the sciences of astronomy and chronology; after having slain an Egyptian who was beating a Jew, he spent his next forty years as a fugitive in Midian, where, laboring as a shepherd for his father-in-law Jethro, he had ample opportunity to hone his abilities as an astronomical observer; and after his encounter with the Burning Bush on Mount Sinai, when he received his Divine commission to lead the Hebrews to freedom in the Promised Land, he applied his knowledge of celestial motion to construct the Jewish Calendar, while wandering through the wilderness with the chosen people for his last forty years.——Eds.]

31. Cf. St. Matthew 5:17.

32. Malachi 4:2.

33. [In Holy Scripture, the word used to denote the Jewish Passover is the same as that used for the Christian Feast of the Resurrection: "Pascha"—Eds.]

34. St. Dorotheos of Gaza, Church Sermons (Thessaloniki: 1991), p. 120.

35. St. John Chrysostomos, Works, Vol. i (1985 ), p. 667.

36. Although the explicit wording of the Seventh Apostolic Canon only forbids the celebration of Pascha "together with the Jews," Patristic interpretation has always taken this to include  a celebration of Pascha before the Jewish Passover as well. Great Friday, the day of the Crucifixion of Christ, fell on Nisan 14, the day of the Feast of the Passover, at the very time when   the Paschal lamb was being slaughtered. To celebrate His Resurrection before the Jewish Passover would thus destroy the important theological connection between these events.

37. The history of which is discussed in Chapter 5.

38. But not the length of the lunar year, since it does not have a constant number of months.

39. The Callipic cycle occurs seven times during the Great Indiction (76x7=532), corresponding to the number of days in a week.

40. Nineteen Julian solar years (each containing 365 days and six hours) equals 6,939 days and eighteen hours, whereas nineteen Jewish lunar years (i.e., 235 lunar months) equals 6,939 days, sixteen hours, thirty-one minutes, and forty-five seconds.

41. The actual difference after 304 years is twenty-three hours and thirty-two minutes.

42. St. John 14:30.

43. Contemporary scientific research shows that over the course of millennia, the velocity of the earth is slowing down, whereas the velocity of the moon, in relation to the earth, is speeding up; however, this difference is so minimal that it in no way affects the goal of exactitude in the Church Calendar.

44. Acts 15:28.

From A Scientific Examination of the Orthodox Church Calendar, by Hieromonk Cassian, eds. Archbishop Chrysostomos and Hieromonk Gregory (Etna, CA: Center for Traditionalist Orthodox Studies, 1998), Ch. 4.