DATING THE BIRTH OF JESUS OF NAZARETH
Dating the year of Christ's birth is as controversial as dating the day of His birth. St. Luke provided several historical references that are helpful in determining Jesus' birth year in his Gospel in Luke 1:5, 2:1-3 and 3:1-2. St. Luke records: In the fifteenth year of Tiberius Caesar's reign, when Pontius Pilate was governor of Judaea, Herod tetrarch of Galilee, his brother Philip tetrarch of the territories of Ituraea and Trachonitis, Lysanias tetrarch of Abilene, and while the high-priesthood was held by Annas and Caiaphas, the word of God came to John the son of Zechariah, in the desert (Luke 3:1-2). The historical record can provide reliable dates for the most of the men mentioned in this passage:
The Roman Emperor Tiberius succeeded his step-father, Augustus Caesar, on the 19th of August in 14AD. Therefore, the 15th year of Tiberius' reign, when St. John the Baptist began his ministry (as the Romans calculated their years) was from August 19th, 28AD to August 18th, 29AD. However, if St. Luke was using the Syrian method of calculating, then the reign of Tiberius would have been from September – October 27AD to 28AD (for a discussion of post-ascension dating see the document "How We Date the Reigns of Old Testament Kings").
St. Luke also provided information concerning Jesus' age when He began His ministry in Luke 3:23: When he began, Jesus was about thirty years old.... That both the priest St. John the Baptist and Jesus, the rightful Davidic king, were thirty years old when they began their ministries is significant: a priest began his full ministerial duties when he was thirty and King David began to rule over Israel when he was thirty years old (Numbers 4:34-35; 2 Samuel 5:4). But this is also information that is useful in calculating Jesus' birth since St. Luke provided the information from the Angel Gabriel that St. John the Baptist was six months older than Jesus: And I tell you this too: your cousin Elizabeth also, in her old age, has conceived a son, and she whom people called barren is now in her sixth month (Luke 1:36-37). From the year calculated as the beginning of St. John the Baptist's ministry and the information concerning the difference in months between John and Jesus' conceptions, it can be calculated that both St. John and Jesus' births were probably in year 3/2 BC.
Testimony supporting the year of Jesus' birth as 3/2BC is also found in the writings of the early Church Fathers. In approximately the year 200AD, St. Clement of Alexandria [150-215AD], head of the Christian catechetical school in Alexandria, Egypt, recorded that Jesus of Nazareth was born in the twenty-eighth year of the reign of the Roman Emperor Caesar Augustus. St. Clement was calculating the beginning of Augustus' reign from the year 727 AUC (a dating system from the foundation of the city of Rome), or in our time, 27BC when the Roman Senate conferred upon him the title "Augustus." St. Clement's calculation gives the date 3BC for Jesus' birth (Christianity and the Roman Empire: Background Texts, Ralph Novak, page 282). St. Clement's calculation was supported by St. Eusebius, Bishop of Caesarea Maritima in the Holy Land, and was recorded in Bishop Eusebius' Church History written in the 4th century AD (Church History, V).
Concerning the month and day of Jesus' birth, St. Clement reported that diverse opinions existed on the identification of both the month and day of the Savior's birth. Some biblical chronologists dated Jesus' birth to April 19th, some May 30th, and St. Clement assigned Jesus' birth to November 17, in what would be in our calendar year 3BC. The Eastern Rite Church Fathers had a long tradition of celebrating the Nativity on January 6th, but there were also other Fathers of the Church who favored December the 25th, and this date became the official celebration of the Nativity of the Savior in the Roman Catholic Church.
There is firm documentary evidence that the birth of the Jesus Christ, our Redeemer and Savior, was being celebrated in Rome as a Christ Mass on December the 25th by the year 336AD. The Eastern Church kept January 6th as the celebration of the birth of Christ until the end of the 4th century and then joined in the observance of the December 25th date, agreeing to celebrate January 6th as the adoration of the Magi. But where and how did the Catholic Church in Rome, guided by St. Peter's successor, settle on December 25th as the day the Savior's birth? Successive attacks on the city of Rome by barbarian armies in the 5th century AD have destroyed any documentation that may have existed, but there may be a way to determine how the date of December 25th came to be the celebrated as the anniversary of the birth of the Savoir.
The earliest mention that I have been able to find identifying the birth of Jesus as December 25th comes from a document entitled The Constitution of the Holy Apostles. Modern scholars continue to debate the date when this early catechism of the Church was written. The Constitution of the Holy Apostles is not as old as the Church document known as the Didache, meaning "The Teaching," that was written between 50-100AD and which is acknowledged as the first catechism of the early Church. Scholars agree that the Didache is the predecessor of the Constitution and the content of that ancient first catechism is, in fact, included within the eight books of the Constitution. There is no doubt, however, that the Constitution of the Holy Apostles is an extremely ancient document written by the Fathers of the Church. Most scholars agree that the first six books cannot be written later than the 300s and some scholars argue that it may have been written in the 200's or even earlier. In the ancient writings of the Church that have survived, it is frequently quoted and appears to have been an updating of the Didache as the official catechism of the universal Catholic Church'just as the Church recently updated the catechism by the publication of the Universal Catechism in 1994. The Constitution of the Holy Apostles contains instructions on the celebration of the Holy Days. Book V, section 3 of the Constitution of the Holy Apostles begins with the subject heading and then addresses the Holy Days including the celebration of the Lord's birthday: ON FEAST DAYS AND FAST DAYS: A CATALOGUE OF THE FEASTS OF THE LORD WHICH ARE TO BE KEPT, AND WHEN EACH OF THEM OUGHT TO BE OBSERVED. XIII. Brethren, observe the festival days; and first of all the birthday which you are to celebrate on the twenty-fifth of the ninth month.... The ancient date of the Constitution can be verified by the fact that its authors were still using the Jewish liturgical calendar. The "ninth month" in the Old Covenant liturgical calendar is our December, since their liturgical year began with the spring equinox which fell in late March/ early April according to our modern calendar, as did the old Roman calendar before Julius Caesar introduced his calendar reform.
For the Jews, the celebration of one's birth was a pagan custom. In the first century AD, religious Jews distained the pagan Roman birthday celebrations and Jewish-Christians may have also felt this prejudice associated with birth celebrations. The prejudice may have changed to acceptance as more Gentile converts embraced Christianity. While it is true that the 25th of December is not mentioned in Scripture, there may be a connection to a Jewish feast day and other Jewish traditions that could identify the birth day of the Christ or which could provide an explanation as to why the Church chose this date. The earliest Fathers of the Church came from a Jewish tradition, and even if they didn't write about Jesus' birth date, they had an oral tradition of Jesus birth, which is the information second century Church Fathers like St. Clement of Alexandria recorded. But it also may have been reasonable for them to deduce from certain Scriptural texts the date of Jesus' birth. There are both New and Old Testament passages that could provide the necessary keys to solve the dilemma of the months of both Jesus' and St. John the Baptist's births.
The angel Gabriel appeared to the priest Zechariah as he was burning incense in the Temple and announced to the old priest that his wife was to bear a son in her old age who would be filled with the Holy Spirit from his mother's womb (Luke 1:8-11). It was shortly after this announcement that St. John the Baptist, the precursor of Christ, was conceived. Many biblical scholars, both ancient and modern, believe Zechariah's service in the Temple was associated with an Old Covenant feast day of national repentance called Yom Kippur (Day of Atonement) and that he was the officiating High Priest offering the incense when the angel announced the birth of St. John. St. John's mission was to call the covenant people to national repentance and he began his mission on or near his 30th birthday. Only the anointed High Priest was to offer the sacrifices on Yom Kippur, but it was unlikely that Zechariah was the officiating High Priest during the Feast of Yom Kipper in the year 4/3 BC since there are comprehensive lists of all the ordained High Priests who served in the Jerusalem Temple from the 2nd century BC to the destruction of the Temple in 70AD, and a priest named Zechariah is not listed. It is, however, likely that Zechariah was the officiating priest performing the rite of burning the sacred incense on the golden Incense Altar in front of the Holy of Holies during the daily service of the sacrifice of the Tamid lambs on the day of Yom Kippur or near to the time of Yom Kippur (the High Priest offered the incense at only one service).
In the 1st century BC, at the time the priest Zechariah, father of John the Baptist, lived and served Yahweh in his priestly duties, there were about 20,000 priests throughout the country'far too many to minister in the Temple at one time. Since the time of King David, the chief priests had been divided into twenty-four separate groups called "courses" that may have been twenty-four families or clans, all of whom were descended from Aaron, the first High Priest. Each group, according to King David's directions (1 Chronicles 24:3-19) took turns serving for a week in the Temple with the exception of the three pilgrim feasts (Exodus 23:14-19; Deuteronomy 16:16; 2 Chronicles 8:13) when the service of all the courses of the chief priests and the Levites (lesser ministers) were required at the Temple. During the two regular daily worship services, lots were drawn to assign the priestly duties. The priest Zechariah was a member of the Abijah division, on duty that eventful day recorded in the Gospel of St. Luke chapter 1. Each morning and afternoon (their "evening" was our afternoon since their day ended at sundown) a priest was to enter the Holy Place in the Temple and burn incense during the daily liturgy of the Tamid sacrifice (Exodus 29:36-42). The third daily lot cast decided who would enter the sacred room, and on this particular day the lot fell to Zechariah.
The drawing of the lot to burn the sacred incense was a once in a life time opportunity for Zechariah. Only a priest who had never been chosen to burn the incense could participate in the drawing of the third lot, but Zechariah's selection was not a chance occasion. God was guiding the events of history to prepare the way for Jesus, the last lamb of sacrifice, the final sacrifice of atonement, to come to earth and to offer Himself for the sins of mankind. And that brings us to the phrase in the Gospel of St. Luke that reads ...all the assembled worshipers were praying outside (Luke 1:10). Some scholars assume that this phrase refers to the gathering of the faithful at the Temple during the offering of the incense on Yom Kippur, but this assumption ignores the fact that twice a day in the Temple, during the most holy part of the worship service, the priest chosen for the honor burned the incense. As the holy smoke carried their prayers to heaven, the congregation gathered in the courtyard prostrated themselves facing the Sanctuary and prayed in silence.
Some biblical scholars focus on the day of Yom Kippur in association with Zechariah's revelation because it was the only Jewish annual feast when the High Priest offered both incense and sacrificial blood on the Altar of Incense. But this assumption ignores the fact that Yom Kippur was not the only day a priest burned incense on the Altar of Incense, and St. Luke's account does not identify Zechariah as an anointed High Priest nor does the Gospel record mention Zechariah smearing blood on the horns of the Incense Altar. On the day of Yom Kippur a great crowd of worshipers would be praying outside the Temple and facing the Holy Place as the anointed High Priest offered incense and smeared the blood of the sacrificed animal on the horns of the golden altar of incense (Leviticus 16:2-4, 11-17). These scholars are assuming that Zechariah was the anointed High Priest officiating on Yom Kippur. But, as we have noted since there are lists of the Jewish High Priests from the time before the reign of King Herod to the destruction of the Temple in 70AD, and Zechariah is not listed as an anointed High Priest on any of those lists, it is unlikely that he was offering incense as the High Priest. Instead, it is more likely that Zechariah was offering incense during either the morning or the afternoon daily liturgy of the Tamid sacrifice. In the offering of the daily Tamid lamb (one in the morning liturgical service and a second at an afternoon worship service at about 3PM), when the incense was offered the people turned toward the Sanctuary and prostrated themselves in prayer as a profound silence filled the Temple. With the exception of the offering of incense during Yom Kippur, there was no other time when a priest came into such close proximity with the presence of God in the Jerusalem Temple. Perhaps Zechariah was offering incense during the daily Tamid worship service either immediately before or immediately after the liturgical service on the annual day of Yom Kippur, or he was offering the incense during a daily liturgy on a day that was near to Yom Kippur. No matter how important an annual feast, it could not take precedence over the Tamid sacrifice which had to be offered twice daily so long as the Sinai Covenant between God and Israel endured (Numbers 28:11; Mishnah: Yoma, 2:4). If John was conceived in the early fall, around the time of Yom Kippur, his birth would be nine months later in the summer.
Biblical scholars have noted that St. John's statement that he must grow less as Jesus grew greater in John 3:30 was illustrated in the traditional dates which the Church celebrates as the dates of their births, with St. John's birth coming after the summer solstice as the days of the year grow shorter and Jesus' birth coming just after the winter solstice as the days of the year grow longer. If this is a clue from St. John recorded in John 3:30 that could be applied to their births, John's conception had to occur nine months earlier in the fall and Jesus' conception six months later in the spring.
Linking Yom Kippur to the announcement of John's birth is significant. The Old Covenant feast day of atonement is a time of national repentance. This was to be John the Baptist's mission; he was to prepare the way for the Messiah by calling the entire covenant people to a baptism of repentance for sin. In the book of Leviticus, Yahweh commanded that this feast was ...to be a lasting ordinance for you: On the tenth day of the seventh month you must deny yourselves and not do any work...[..]. Because on this day atonement will be made for you to cleanse you. Then, before Yahweh, you will be clean from all your sins (Leviticus 16:29-30). According to the Jewish liturgical calendar this day of national repentance had to fall prior to the autumn equinox; the next Jewish feast, the Feast of Tabernacles (Sukkot), had to fall five days after Yom Kippur during the full moon either on or the first full moon after the autumnal equinox (the date of the autumn equinox is September 23rd according to our modern calendar). Since it has long been a tradition in the Church that the angel came to the priest Zechariah at a time association with the Old Covenant feast of Yom Kippur, it is interesting that the Church has for centuries celebrated the feast of St. John the Baptist on the day of his birth which the Church has determined is June the 24th (only St. John, Jesus, and the Virgin Mary have feast days associated with their births). If John's birth occurred on June 24th, according to the Church's liturgical calendar, then his conception would have been nine months earlier in September, near the time of the observance of the Feast of Tabernacles and just after Yom Kippur.
But how does that information help to determine the birth of Jesus? When the angel Gabriel came to Mary he informed her that her cousin Elizabeth was already six months with child: Even Elizabeth your relative is going to have a child in her old age, and she who was said to be barren is in her sixth month (Luke 1:36). Six months from the autumnal equinox on September 23rd, by our calendar, gives us a date of March 23rd . The Church celebrates the Annunciation March 25th, very close to the spring equinox. When you add nine months to March 25th you have December 25th as the birth of our Savior. Is it a coincidence that all these significant dates associated with St. John and Jesus fall near the year's four divisions? No, our seasons and the momentous events associated with the coming of our Savior are all part of God's great plan since the creation of the world. Our seasonal divisions were established after the Flood (see Genesis 8:22) and the cycles of the moon determined the Old Covenant liturgical calendar.(1)
There is one more piece of evidence that may support the theory that the Church used this information to determine the birth of Jesus. According to the Fathers of the Church there was a tradition that Jesus died on the cross on the same day of the year that he was conceived by the Holy Spirit. Jesus died on the Feast of Passover, which falls during the first full moon after the spring equinox (end of March or early April is the yearly spread in calculating the date according to the moon's cycle), and the Feast of the Annunciation has always celebrated in the Church on March 25th!
If the Church has determined that Jesus was born December 25th, why is it that the beginning of our civil calendar year, calculated by a Catholic Abbot in the 6th century AD (our liturgical year begins at Advent in early December), begins on January 1st? In 525AD mathematician, Abbot Dennis the Short, rejected the old Roman calendar which was dated from the founding of the pagan city of Rome and established a new calendar, which he dated from what he calculated as the year of the birth of Christ (designated as year 1 Anno Domini= "in the year of our Lord"). He decided to date the beginning of the civil calendar year with Jesus' entrance into the Old Covenant faith according to the Old Covenant Law. This event was commanded, since the time of God's covenant with Abraham, to take place eight days after the birth of a male child (Genesis 17:9-12; 21:2-4). Counting December 25th as day one, which was the ancient custom since there was no concept of 0-place value, the eighth day was January 1st.(2)
It is a shame that the calculations Dennis used to date the year of Jesus' birth no longer survive. Other Christian scholars disagreed with Dennis' year of birth calculations for Christ, supporting instead the testimony of Fathers of the Church like St. Clement of Alexandria (3rd century AD) and Bishop St. Eusebius of Caesarea in the Holy Land (4th century AD). Both these early Church Fathers agreed that Jesus was born three years earlier (see Clement of Alexandria's Stomata, I and Eusebius' History of the Church chapter 5). Eusebius wrote in his Church History: It was in the forty-second year of the reign of Augustus and the twenty-eighth after the subjugation of Egypt and the death of Antony and Cleopatra. These calculations place Jesus' birth in 3BC (BC = Before Christ). Eusebius was dating Augustus' reign from the death of Julius Caesar, in our time = 44BC and the deaths of Antony and Cleopatra in 30AD, our time. Dates before the year 1BC and 1AD (the year designated by Dennis the Short as the year of Christ's birth) are counted in greater numbers counting backward from Christ's birth and in greater numbers counting forward from His birth. There is no year 0. In calculating the dates of ancient times it is important to remember that it was not until the Middle Ages that the mathematical concept of a 0-place value was introduced into the West, and this concept was not employed in Jesus' time, therefore, in counting sequences in ancient times the count always including the first in the sequence as #1. This was why Sacred Scripture records Jesus was in the tomb for three days instead of two days from Friday to Sunday (Luke 24:7, 46; Acts 10:40).
Today most modern scholars have based the year of Jesus' birth on a calculation of a lunar eclipse originated by the report of the 1st century AD Jewish priest/historian Flavius Josephus that Herod the Great died after a lunar eclipse and before the annual remembrance feast of the Passover (Antiquities of the Jews 17.6.4 ). The Feast of the Passover and all the sacred feasts were based on the lunar calendar. The annual remembrance of the Passover sacrifice was commanded by Yahweh to commence on the 14th of Nisan, with the sacrificial meal celebrated on the night of the full moon on the 15th (Exodus 12:6,-8; Leviticus 23:5-6) which came after the vernal equinox.(3) In 1630, the great astronomer Johannes Kepler (d. 1630), in trying to identify Jesus' birth year through Josephus' information concerning Herod's death associated with a lunar eclipse, identified the year 4BC as the year of a partial lunar eclipse on March 12/13, with the Jewish Passover twenty-nine days later on April 11th . He also found that there was a total lunar eclipse in 5BC, but with a lapse in time of seven months until the Passover this date seemed unlikely. Kepler also proposed that St. Matthew's account of the star refers to several extraordinary conjunctions of Jupiter and Saturn that took place in 7BC.
Since the late 19th century most biblical scholars have accepted Kepler's discovery as proof that Herod died in 4BC and therefore assume that Jesus must have been born in year 7 or 6BC, completely ignoring St. Luke's testimony in Luke 3:1-2 in determining the year of Jesus' birth. Recently, however, modern astronomers using more sophisticated and accurate instruments have calculated that in year 1BC there was full lunar eclipse viewed from Jerusalem on the night of January 9/10 and the Passover Feast of that year was celebrated just twelve and a half weeks later on April 8th. This information has caused some biblical scholars to reassess the calculations of Jesus' birth year from 7BC to the year 3/2BC, in agreement with Sts. Clement and Eusebius and with St. Luke's testimony that St. John (and Jesus) were 30 years old in the 15th year of the Emperor Tiberius, which would be the year 28AD, providing a birth year of 3/2BC.
Dr. Ernst Martin has also discovered that there was an even more striking stellar event than the one Kepler identified in 7BC. During the year 2BC the conjunction of Jupiter and Venus must have caused a spectacular stellar display. With Venus rising in the east the conjunction with Jupiter would have appeared in the sky as a single brilliant light. The inspired writer of the New Testament book of Revelation refers to Jesus as "the bright morning star" in Revelation 22:16, a reference which links the planet Venus, the morning star, to Christ and any stellar event involving the giant planet Jupiter was always viewed by the ancients as the birth of a king, as the event of the sign in the stars was interpreted by the Magi. Dr. Martin's Christmas star theory has been accepted by many of the world's prestigious observatories, including the Griffith Observatory in Lost Angeles and is featured in their annual Christmas program.
The date of Herod the Great's death based on the eclipse of the moon which took place in 4BC would place Jesus' birth sometime between 7 and 4BC and does not agree with St. Luke's information of the beginning of St. John and Jesus' ministries in the Gospel of Luke. However, Clement's information of a 3/2BC date supports St. Luke's account and is also supported by the modern astronomers' finding that a full lunar eclipse occurred in year 1BC, which could be the lunar eclipse Josephus referred to, with a spectacular conjunction of planets in 3/2BC, which could be the "star" of Bethlehem. If the 1BC lunar eclipse is what Josephus associated with Herod's death, then the 3/2BC birth date for Jesus is in agreement with the biblical account.
It has also been determined that scribal error compromised other accounts first century AD Jewish historian Flavius Josephus' dates concerning Herod's family. Copies of his history after the year 1544 indicate Herod actually died later than previously believed in the year that would correspond to our year 1BC. In all copies of Antiquities of the Jews 18.106 prior to 1544, Josephus placed Herod the Great's son Philip's death in the twenty-second year of the reign of the Roman Emperor Tiberius, after ruling for thirty-seven years after the death of his father Herod the Great instead of in the twentieth year of Tiberius as recorded in many copies of the history after 1544. The copyist evidently mistakenly failed to write 22 and instead recorded 20 years and the mistake was repeated by other copyist. The older account from Josephus' history, therefore, places the death of Herod in the year 1BC our time (see The Works of Josephus, page 483, footnote c). If King Herod died in year 1BC, according to our modern calendar, and if Herod believed Jesus to be just under 2 years old when he ordered the murder of the babies in all villages around Jerusalem, then a birth date of fall/winter 3/2BC for Jesus would agree with both St. Clement's and Bishop Euseibus' accounts as well as the calculations that can be made from the information provided in the Gospel of St. Luke. All the available information supports a birth date for Jesus of Nazareth on about December 25/January 6th, 3/2BC, with the beginning of His ministry when He was thirty years old in 28AD and His death during the Passover of 30AD.
Michal Hunt copyright Dec. 1999; revised February 2004, June 2007, December 2008
1. The vernal equinox occurs when the sun changes from south to north of the celestial equator, appearing to cross the celestial equator and intersecting the constellation Pisces. The sun appears to cross the celestial equator at this point on about March 21st each year. This is the vernal equinox, which means the "green time of equal nights and days." Because of the sun's position at this time of the year over the earth's equator, the day is evenly divided for a brief period between sunlight and darkness. At this time, spring begins in the northern hemisphere and autumn begins south of the equator. The opposite point of intersection is in the constellation Virgo where the sun appears to cross the equator from north to south. This is the autumnal equinox. The sun reaches this point each year on about September the 23rd. Autumn begins north of the equator and spring comes to the southern hemisphere. The solstice, on the other hand, marks the extreme northern or southern position of the sun in its apparent annual journey. The sun appears to reach its most northern position, known as the summer solstice, on about June 21st when summer begins north of the equator. The opposite point is the winter solstice, is reached on about December the 21st. This marks the most southern position of the sun and the beginning of winter in the Northern Hemisphere. The summer solstice is located at the intersection of the stars of Gemini and the winter solstice is marked by the crossing in the constellation of Sagittarius. The procession of the earth has shifted the solstices in their positions. In ancient times the summer solstice was in the constellation of Cancer and the winter solstice in Capricorn.
2. Christianity and the Roman Empire , page 282; Calendar: Humanity's Epic Struggle to Determine a True and Accurate Year, page 189; Mapping Time: The Calendar and its History, pages 77-78, 81. This is why Scripture records that Jesus was in the tomb three days from Friday to Sunday, instead of two days as we would count it. The ancients counted time the way we count objects.
3. Philo of Alexandria, 1st century AD Jewish theologian wrote: And there is another festival combined with the feast of the Passover, [...]. This month being the seventh [in the civil calendar] both in number and order, according to the revolutions of the sun, is the first in power; on which account it is also called the first in the sacred scriptures. And the reason, as I imagine, is as follows. The vernal equinox is an imitation and representation of that beginning in accordance with which the world was created. [..]. And again, this feast is begun on the fifteenth day of the month, in the middle of the month, on the day which the moon is full of light, in consequence of the providence of God taking care that there shall be no darkness on that day (Special Laws, II. 150-155).
1. Fr. John Laux, M.A., Church History
2. The Ante-Nicene Fathers: Vol.7, Apostolic Teaching and Constitutions
3. The Age of Faith, Will Durant.
4. Eusebius, Church History
5. Clement of Alexandria, Stromata
6. Flavius Josephus, Antiquities of the Jews
7. Jack Finegan, Handbook of Biblical Chronology
8. The Works of Josephus, translated by William Whiston, Hendrickson Publishers, 1998.
9. Christianity and the Roman Empire: Background Texts, Ralph M. Novak, Trinity Press International, 2001.
10. Bible Review: December 1999, "Why 2K? The Biblical Roots of Millennialism," by James Tabor, pages 16-27.
11. Calendar: Humanity's Epic Struggle to Determine a True and Accurate Year,
12. Mapping Time: The Calendar and its History