Mathematical Consistency

The Book of Mormon contains multiple calendar systems¹ that collectively feature hundreds of sequentially consistent references to time.² In some cases, those references are accompanied by additional statements about the passage of years, such as an individual’s age or the duration of a treaty. In other circumstances, the reckoning of a date is given for multiple calendars simultaneously. These situations provide opportunities to test the internal consistency of the Book of Mormon’s chronology, typically via basic mathematical calculations.³ The following sections summarize nearly a dozen such occasions in the order that they show up in the text.

1. Mosiah’s Reign

Mosiah, the son of King Benjamin, “began to reign in the thirtieth year of his age, making in the whole, about four hundred and seventy-six years from the time that Lehi left Jerusalem” (Mosiah 6:4). More than 20 chapters later, it is reported that “Mosiah died also, in the thirty and third year of his reign, being sixty and three years old; making in the whole, five hundred and nine years from the time Lehi left Jerusalem” (Mosiah 29:46). The combination of data given in these verses involves two mathematically correct and mutually supporting calculations:

• Mosiah began his reign when he was 30 years old and died in the 33rd year of his reign. Adding these years (30 + 33) results in 63 years, which correctly corresponds to the age given for Mosiah when he died. One could also subtract 33 years from 63 years to verify the accuracy of Mosiah being 30 years old when he began his reign.
• Mosiah began his reign 476 years after Lehi left Jerusalem, and his reign ended 509 years from that same time. Subtracting these years (509 - 476) again equals 33 years, which correctly relates to the amount of years given for Mosiah’s reign.

The following chart provides a helpful way to look at the data and calculations involved:

 

2. Ammonihah’s Reoccupation

After the city of Ammonihah was destroyed in the “eleventh year of the reign of the judges” (Alma 16:1), it is reported that “so great was the scent thereof that the people did not go in to possess the land of Ammonihah for many years” (v. 11). This comment is corroborated many chapters later when Mormon noted that by “the eleventh month of the nineteenth year,” the city of Ammonihah had been partially rebuilt (Alma 49:1–3).

Since Moroni’s fortification projects were in response to Amalickiah’s dissension (Alma 48:8–9), and since Amalickiah’s dissension took place in the 19th year,⁴ it seems likely that Ammonihah’s renovation took place in this same year. This, in turn, would mean that a significant number of years (approximately 8) had indeed passed between Ammonihah’s destruction and reoccupation, just as mentioned 33 chapters earlier in Alma 16:1.

3. A Fourteen-Year Mission

Before giving a lengthy account of the missionary efforts of the sons of Mosiah, Mormon noted that “they had been teaching the word of God for the space of fourteen years among the Lamanites” (Alma 17:4). Several verses later, Mormon mentioned that they had “taken leave of their father, Mosiah, in the first year of the judges” (Alma 17:6). And at the conclusion of the previous chapter, Mormon declared: “thus ended the fourteenth year of the reign of the judges over the people of Nephi” (Alma 16:21). Since the sons of Mosiah left in the 1st year of the reign of the judges, and since Mormon recently reported that the 14th year of the reign of the judges had ended, it means that Mormon’s description of the sons of Mosiah serving “for the space of fourteen years” is consistent with the surrounding chronological data.

4. The Sons of Mosiah Left in the First Year of the Reign of the Judges

As noted in the previous section, Mormon stated in Alma 17:6 that the sons of Mosiah left their father “in the first year of the judges; having refused the kingdom which their father was desirous to confer upon them, and also this was the minds of the people.” This timeframe works out based on previous data.

In Mosiah 28:9, it is reported that the sons of Mosiah “took their journey into the wilderness to go up to preach the word among the Lamanites.” No date is given, but immediately after reporting their departure, Mormon explained that Mosiah conferred the records and sacred things upon Alma (vv. 10–19). Then, the very next chapter initiates the first year of the reign of the judges (Mosiah 29:44). This suggests that the sons of Mosiah left sometime close to the government transition, which means they possibly left at an earlier part of the same year. While this analysis doesn’t conclusively verify Mormon’s statement in Alma 17:6, it renders it entirely plausible and consistent with the available data.

5. Synchronization of the Reign of Judges with time from Lehi’s Departure

In 3 Nephi 1:1 it is reported that “the ninety and first year had passed away and it was six hundred years from the time that Lehi left Jerusalem.” These dates relate back to the last year marker since Lehi’s departure (LD) from Jerusalem, which is found in Mosiah 29:46: “And it came to pass that Mosiah died also, in the thirty and third year of his reign, being sixty and three years old; making in the whole, five hundred and nine years from the time Lehi left Jerusalem.”

According to Mosiah 29:44, this year (509 LD) was also the 1st year of the reign of the judges (RJ), and since 3 Nephi 1:1 says that the passing of the 91st year (RJ) coincided with the passing of 600 (LD), it means that these dates are all mathematically related and testable: 509 + 91 = 600. The same would be true for the statements in 3 Nephi 2:5–7, which note that the passing of 100 years (RJ) coincided with 609 years (LD): 509 + 100 = 609. How many readers, though, notice that these dates in 3 Nephi are consistent with a date given all the way back in Mosiah 29?

6. Synchronization of All Three Nephite Calendars

As noted in the above section, 3 Nephi 1:1 reports that “the ninety and first year had passed away and it was six hundred years from the time that Lehi left Jerusalem.” Later, in the same year, the sign prophesied of by Samuel the Lamanite was fulfilled, making this also the first year in the new calendar (3 Nephi 1:15).⁵ In 3 Nephi 2:5–7, Mormon gives yet another date for all three Nephite calendars simultaneously:

And also an hundred years had passed away since the days of Mosiah, who was king over the people of the Nephites. And six hundred and nine years had passed away since Lehi left Jerusalem. And nine years had passed away from the time when the sign was given, which was spoken of by the prophets, that Christ should come into the world.

Because a date is given (or in one circumstance, implied) for all three calendars on both occasions, it makes it possible to check them for accurate synchronization. And sure enough, the second date produces the correct mathematical relationship for all three calendars, as demonstrated in the following chart (in each case, 9 years had passed away):

 

7. Seven Years of Consolidation

During a conflict with the Gadianton robbers, the Nephites on one occasion gathered together provisions of every kind, including many types of animals, so “that they might subsist for the space of seven years, in the which time they did hope to destroy the robbers from off the face of the land; and thus the eighteenth year did pass away” (3 Nephi 4:4). This description is noteworthy because two chapters later, after the Nephites had conflicts with the robbers for precisely seven years (comprising the 19th–25th years), Mormon emphasized that the consolidation was over and that the Nephites returned to their own lands:

And now it came to pass that the people of the Nephites did all return to their own lands in the twenty and sixth year, every man, with his family, his flocks and his herds, his horses and his cattle, and all things whatsoever did belong unto them. And it came to pass that they had not eaten up all their provisions; therefore they … did return to their own lands and their possessions. (3 Nephi 6:1–2)

8. Christ’s Disciples Had All Gone to Paradise

Sometime during or after the 34th year since the sign of Christ’s birth (3 Nephi 10:18), Jesus visited His disciples after they had gone about building up His church among the people. In response to Jesus’ invitation to share the desires of their hearts, several disciples asked to come to Christ’s kingdom after they had “lived unto the age of man” (3 Nephi 28:2). Jesus then declared, “Blessed are ye because ye desired this thing of me; therefore, after that ye are seventy and two years old ye shall come unto me in my kingdom” (v. 3). Later, in 4 Nephi, Mormon remarked on the fulfillment of these words, noting that “even an hundred years had passed away, and the disciples of Jesus, whom he had chosen, had all gone to the paradise of God, save it were the three who should tarry” (4 Nephi 1:14).

Because the 34^th year is the earliest that Jesus would have given this promise to the disciples, it means that, at most, about 66 years had passed away since Christ had made the statement (100 - 34 = 66). This, in turn, means that in order for the disciples to have died (or possibly to have been translated) when they were 72 years old, they would have needed to be at least six years old when Christ made the promise to them (72 - 66 = 6).

Because this seems like a very safe assumption to make (it is hard to imagine Christ calling disciples who were younger than 7 years old), it means that Mormon’s statement about the disciples entering paradise is consistent with the available chronological data. Although this correlation is less precise than others, it still checks out. Each of the disciples (except the three who were to tarry) should have reached the age of 72 sometime before the passing of the 100th year.  

9. Amos Kept the Plates for 84 Years

After noting that “an hundred and ten years had passed away” since the sign of Christ’s birth (4 Nephi 1:18), Mormon noted that Nephi had died and that a man named Amos kept the records in his stead for “eighty and four years” (v. 20). Mormon then noted that “Amos died also, (and it was an hundred and ninety and four years from the coming of Christ) and his son Amos kept the record in his stead (v. 21). When the first time marker (110 years) is subtracted from the second marker (194 years), the total is 84 years, consistent with the amount of time that Mormon said Amos kept the record.

10. Mormon’s Age

In 4 Nephi 1:48, Mormon noted that “when three hundred and twenty years had passed away, Ammaron, being constrained by the Holy Ghost, did hide up the records which were sacred.” Then, when introducing his own record, Mormon also noted that he was “about ten years of age” when “Ammaron hid up the records unto the Lord” (Mormon 1:2). When combining these passages, readers can conclude that Mormon was about 10 years old after the passing of the 320th year.

This data can be compared to Mormon’s explanation in Mormon 2:2, which also gives his age and the date: “Therefore it came to pass that in my sixteenth year I did go forth at the head of an army of the Nephites, against the Lamanites; therefore three hundred and twenty and six years had passed away.” This passage is consistent with the previous data in that the passing of six calendar years accurately corresponds to Mormon being six years older, as demonstrated in the following chart

11. Ten Year Peace Treaty

After describing a series of battles, Mormon reported that “in the three hundred and fiftieth year we made a treaty with the Lamanites and the robbers of Gadianton” (Mormon 2:28). Mormon then explained that “the Lamanites did not come to battle again until ten years more had passed away” (Mormon 3:1). Several verses later, it is reported that “after this tenth year had passed away, making, in the whole, three hundred and sixty years from the coming of Christ, the king of the Lamanites sent an epistle unto me, which gave unto me to know that they were preparing to come again to battle against us” (v. 4).

The amount of text separating the report of the 350^th and 360^th years is not particularly impressive, and these types of round numbers (350 and 360) in a base 10 system would likely be easier to remember. Nevertheless, the math checks out. Mormon mentioned the 350^th year passed, discussed a 10-year peace treaty, and then mentioned that the treaty was over and that 360 years had passed (360 - 350 = 10).

Accounting for a Possible Error in Samuel’s Five-Year Prophecy

While almost all testable chronological data in the Book of Mormon is mathematically accurate, there is one interesting exception. In Helaman 14:2–3 Samuel the Lamanite delivered the following prophecy: “Behold, I give unto you a sign; for five years more cometh, and behold … in the night before he cometh there shall be no darkness, insomuch that it shall appear unto man as if it was day.” One chapter earlier, in Helaman 13:1–2, it is reported that Samuel delivered this prophecy “in the eighty and sixth year.” With this information in hand, readers would naturally expect for the prophecy to be fulfilled sometime in the 91st year. Mormon, however, reported that the sign (a night without darkness) appeared sometime in the 92nd year (3 Nephi 1:1, 15).

One important consideration is that the timing of Samuel’s prophecy is disputed in the text itself. Some people felt the time for its fulfillment had passed, while others clearly thought there was a way for it to still be fulfilled (3 Nephi 1:5–7). This suggests that rather than being a simple error on the part of the text’s author, editor, or translator, something else was going on in the way the Nephites were reckoning their time.

The discrepancy can possibly be explained when this narrative is placed in an ancient Mesoamerican context, where two calendars—one using 360-day years and another using 365-day years—were used simultaneously.⁶ If Samuel’s prophecy was given using the 365-day calendar, but Nephite years were counted using the 360-day calendar, then the slight delay for the fulfillment of the prophecy would be understandable. Other solutions may arise from unknowns involving the redaction history of Samuel’s words, the timing of Samuel’s words (maybe they were given on separate occasions with elapsed time), and a potential difference in the part of the year in which the Nephites’ separate calendar systems began.⁷

Conclusion

In nearly every instance, the Book of Mormon’s chronological data is consistent when that data can be tested by additional textual evidence. The only exception (Samuel’s five-year prophecy) is recognized in the text itself as a possible discrepancy and may be accounted for in several different ways.

Verifying these chronological relationships, however, is not always a straightforward process. Many of the dates involved aren’t numbers that are easy to remember or calculate (meaning they don’t end in 0 or 5). On several occasions, the relevant data must be extracted from multiple verses found in separate locations. And nearly half of the sections in this article (#1, #2, #4, #5, #8) involve dates or data that are separated by thousands of words of text. That means that a significant amount of time—in some cases many hours or multiple days—would have transpired between the dictation of the relevant passages of text.⁸ It should also be remembered that Joseph Smith claimed to only have been instructed in the “ground rules” or arithmetic.⁹ He was not well-educated in 1829 when he translated the Book of Mormon.¹⁰

All in all, the textual and mathematical accuracy of the Book of Mormon’s chronology, especially in light of the constraining circumstances of its translation, makes it a noteworthy aspect of the book’s complexity.¹¹

Daniel L. Belnap, “‘There was One Samuel’: Possible Multiple Sources for the Samuel Narrative,” in Samuel the Lamanite: That Ye Might Believe, ed. Charles Swift (Salt Lake City and Provo, UT: Deseret Book and BYU Religious Studies Center, 2021), 260–263.

Neal Rappleye, “‘The Time is Past’: A Note on Samuel’s Five-Year Prophecy,” Interpreter: A Journal of Latter-day Saint Faith and Scholarship 29 (2018): 21–30.

John P. Pratt, “Book of Mormon Chronology,” in Encyclopedia of Mormonism, 4 vols., ed. Daniel H. Ludlow (New York, NY: Macmillan, 1992), 1:169–171.

Mosiah 6:4 Mosiah 28:9–19Mosiah 29:44Mosiah 29:46Alma 16:1Alma 16:11 Alma 16:21Alma 17:4Alma 17:6Alma 48:8–9Alma 49:1–3 Helaman 13:1–2Helaman 14:2–3 3 Nephi 1:1 3 Nephi 1:5–73 Nephi 1:153 Nephi 10:183 Nephi 2:5–73 Nephi 2:5–73 Nephi 28:2–33 Nephi 4:43 Nephi 6:1–24 Nephi 1:14 4 Nephi 1:184 Nephi 1:204 Nephi 1:48Mormon 1:2Mormon 2:2Mormon 2:28Mormon 3:1Mormon 3:4​​​​​​​

Mosiah 6:4

Mosiah 28:9–19

Mosiah 29:44

Mosiah 29:46

Alma 16:1

Alma 16:11

Alma 16:21

Alma 17:4

Alma 17:6

Alma 48:8–9

Alma 49:1–3

Helaman 13:1–2

Helaman 14:2–3

3 Nephi 1:1

3 Nephi 1:5–7

3 Nephi 1:15

3 Nephi 10:18

3 Nephi 2:5–7

3 Nephi 2:5–7

3 Nephi 28:2–3

3 Nephi 4:4

3 Nephi 6:1–2

4 Nephi 1:14

4 Nephi 1:18

4 Nephi 1:20

4 Nephi 1:48

Mormon 1:2

Mormon 2:2

Mormon 2:28

Mormon 3:1

Mormon 3:4