That’s actually a very fascinating subject which has interested scholars in many different fields (and not just Biblical scholars.) It’s been decades since I studied such things in grad school but I can give a few general answers from what I do recall. These phenomena are consistent with the many cultural differences I learned about in the course of comparative linguistics and language translation.
Let’s begin by noticing some of the ways cultures differ in terms of counting.
Suppose a newspaper in Fredonia reports that “Unrelenting Torrential Rains Plague Capital City for 48 Hours”. On the other side of the continent a newspaper in Sylvania has the headline “Three Days of Torrential Rains Endanger Residents of Fredonian Capital.” Which is correct? (Obviously, 48 hours is two days, not three.)
How does one reconcile the difference? In nation Sylvania, the duration of such events are usually measured in days of the week, so a rainstorm which begins on Wednesday and ends of Friday is a three day event. (Very few cultures would count in terms of regarding Wednesday as “Day 0” and Friday as “Day 2”, but that convention is certainly
just as possible and certainly logical.)
Yes, cultures use numbers and counting conventions differently. For example, in some cultures something which began at 11 p.m. on Monday (such as a power outage) and ended at 1 a.m. Wednesday morning was a three day event—because it involved three days of the week. Another culture will count the event as two days long because it lasted longer than 24 hours but less than or equal to 48 hours. Yet another culture will count it as a one day event because it lasted only slightly more 24 hours. (After all, a 26 hour event is far closer to one day in duration than it is two days in duration! By the way, some cultures round their numbers to the nearest integer while other cultures may always round their numbers down. Thus, 1.4 may be rounded to 1 in Fredonia but rounded to 2 in Sylvania. So a Fredonia textbook may state that “King Gustus reigned for only one year” while in Sylvania a history book may say “King Gustus of Fredonia ruled for two years.”)
So which culture in the previous paragraph’s examples is “correct” according to the average American today? Does it matter? Obviously, all of those conventions are correct within their own cultural context.
By the way, to use a slightly different example, if a 14 month old child was mentioned in a news story in Fredonia, the headline might say “One-Year-Old Succumbs to Rare Virus”—but in Sylvania the headline is “Rare Disease Overtakes Fredonian Two-Year Old.” Each headline is truthful and easily understood in context.
I once dealt with a confusion of this sort with a man from a mission field in Africa. One account claimed he was age 58, another said age 59. To make matters even more confusing, a missionary who had lived in the village remembered the man saying that he was sixty years old—but when the missionary returned for a visit two years later, the man claimed that he was seventy years old. How can this mess be reconciled? Was somebody lying?
As it turned out, the “age 58” was from a reckoning system familiar to Americans where a person of “58 years, 5 months” is considered fifty-eight years old. The “age 59” was because he was living his fifty-ninth year, which is the favored convention in some other cultures. (That is, a newborn baby is living in his/her first year until the first birthday. A fourteen-month-old baby is in his/her second year of life. Thus, a man who died one day after his 58th birthday is considered age 59 and that may appear on his tombstone. Is that tombstone erroneous?) But how could a man be sixty years old and then be seventy years old two years later? Easy: He became a great grandfather. Some cultures use numerical designations to reflect social status and/or generational relationships. Indeed, if a revered elder in a village is elevated to chief, he may be given the title of “great great grandfather” or even “seventy-something” [my rough translation] to reflect his superior and honored status. That could happen even if he is only age 62 and he has zero great great grandchildren!
By the way, I believe that such a cultural honorific explanation may explain the age of Moses upon his death as “120 years.” I’m NOT claiming that it absolutely could not be literally true. I’m saying that I think it possible that this was simply a way a designating his revered status and special position. It may also a reflect a sexagesimal number system where 120 years consists of two sixties (i.e. 20 in sexagesimal), which is a revered number. Unfortunately, unlike today, scholars of ancient history can’t interview the natives to understand unambiguously their cultural conventions.
We are only getting started. In South Korea years are reckoned according to the Western calendar, so the year is 2020. In North Korea years are reckoned according to the years of founder Kim Il-sung, which explains Juche 109. Fortunately, the North Korean calendar uses the same January 1 as the first day of the New Year. But what if their new year (Juche) began on March 1? That would have made for very tricky conversions between dates in North Korea and South Korea. Indeed, that is exactly the kind of complications we have with ancient Roman history because their year began on March 1, so that their year-count advanced to the next integer on that date. (Have you ever wondered why October is our tenth month of the year, even though the Latin morpheme “octo-” means eight? Likewise the incongruities multiply with September, November, and December, the alleged tenth month. If the Bible spoke of the twelfth month of the year but used the name “December”, meaning “tenth month”, would that be listed at the Skeptics Annotated Bible website as a “Bible error”? Probably.)
If you want to pursue calendar confusion further, check out the change from the Julian calendar to the Gregorian calendar—and how the new calendar was adopted in various countries on different dates. (That gradual change still gives scholars of Russian history absolute fits, for example!)
When Does a King’s Reign Begin?
Some cultures confuse us with numbering systems for a kings’ reigns which overlap–while in other systems they cannot overlap. For example, Fredonian conventions may dictate that if a king dies in November and his son takes the throne that same day, the year 2019 may be BOTH the last year of King Moe’s reign and the first year of King Moe II’s reign. Yet, in Sylvania the chroniclers refuse to reckon the same year under two different reigns. Worse yet, in neighboring Nowhereania, a king’s reign begins when he is named as heir to the throne—so in that system a King Moe’s reign may overlap with King Moe Jr’s reign by decades!
A good historian must be prepared for even more complications. Suppose a king dies when his successor is under-age. In such cases, a regent may be appointed until the successor becomes an adult and capable of taking full powers of the position. Does the reign of that new king begin when the previous king dies or when he comes of age and the regent is dismissed? When that new king dies many years later, did he reign 80 years or 68 years? It depends on whether one counts the regency or only the years of full royal powers. (And how does one treat partial years?) Does a reign only refer to the years of full power or the entire period when the kingly crown was ceremonially worn? This is indeed a complication with Old Testament reckonings of reigns.
As you can see in the above illustrations, in most such cases, figurative interpretations per se have nothing to do with the discrepancies.
All of that said, I would also hasten to add that numbers are one of the more “fragile” components of ancient texts. I’m inclined to assume that copyist errors arise quite easily over the centuries in some contexts, though that is more of a factor with large numbers (such as counting national and tribal populations and the size of armies.)
One other thought: The Ancients Weren’t Stupid.
We moderns immediately jump to the conclusions that the ancients were in error when something doesn’t make sense to us. My favorite example is the silly complaint that the Bible is wrong about the number of legs on a grasshopper. Do we really think it likely that the ancients were unable to count the appendages of a pest which could spell the difference between feast and famine? Seriously? (See the Skeptics Annoted Bible for yet another idiotic face-palm.)
Any competent comparative linguist can explain that cultures classify and label things differently. We today may look at a grasshopper and see six legs—but someone in another cultures sees four appendages of virtually identical structure and calls them “legs” while noticing two very different and very large appendages toward the posterior and calls them “springs” or “jumpers.” (After all, those two big things in the back don’t look anything like the four in the front and the grasshopper doesn’t use them in the same way.) So one culture may speak of six legs while the others describes the same six appendages as four legs and two jumpers. If we could interview native speakers of that ancient culture, we could easily resolve such issues. Our alternative is to assume that ancient writers were somehow incapable of counting appendages on a insect very familiar within their everyday lives. Seriously? Let’s not be so foolish.
One more example: As a young teaching professor (before I moved into research and administration full-time) I had some fascinating conversations with my international advisees. I remember one of my students from China would get confused about various American phenomena. For example, he didn’t understand the difference between a president being elected and a president being inaugurated. (To him, both meant “to begin”, in essence.) So he thought Ronald Reagan became the new president in 1980, rather than almost three months later when he was inaugurated. I remember him asking me “How does that work when you have two presidents, Carter and Reagan, at the same time? Do both live in the White House?” He wasn’t incompetent at counting. He just didn’t understand terminology of a foreign culture.)