We corresponded briefly in the spring of 2021, and you kindly answered some questions. Recently, I started studying Jeremiah’s prophecy of 70 years of desolation for Judah and tried to determine when the prophecy was fulfilled. I used your technique for calculating the duration of a prophetic era; the prophecy was fulfilled (not surprisingly) to the day. I have not found this result elsewhere; I thought that you might be interested.
Jeremiah prophesized 70 years of desolation for Judah. When did this period start and end?
(ESV) Jeremiah 25:11 “This whole land shall become a ruin and a waste, and these nations shall serve the king of Babylon seventy years. 12 Then after seventy years are completed, I will punish the king of Babylon and that nation, the land of the Chaldeans, for their iniquity, declares the LORD, making the land an everlasting waste.”
Start of 70 years of Desolation
The prophecy started with the beginning of the siege of Jerusalem on the 10th day of the 10th month of the ninth year of the reign of Zedekiah, which is recorded in 2 Kings 25:1.
(ESV) 2 Kings 25:1 “And in the ninth year of his reign, in the tenth month, on the tenth day of the month, Nebuchadnezzar king of Babylon came with all his army against Jerusalem and laid siege to it. And they built siegeworks all around it.”
(ESV) Jeremiah 39:1 “In the ninth year of Zedekiah king of Judah, in the tenth month, Nebuchadnezzar king of Babylon and all his army came against Jerusalem and besieged it.”
The 10th day of the 10th month would be 10 Teveth on the Hebrew calendar. Identifying the year requires determining which year corresponds to the 9th year of the reign of Zedekiah.
Thiele, in his The Mysterious Numbers of the Hebrew Kings, calculated the years of the reigns of the Hebrew kings of the Old Testament. His analysis (page 184) showed that the siege started on 15 January 588 BC, which corresponds to 10 Shevat 3173. Shevat, however, is the 11th month, while Scripture tells us that the siege started on the 10th month—which is Teveth. Thiele appears to be wrong on his calculation of the Julian date.
Since Thiele’s focus was on the years of the reigns and not the conversion of specific dates into Julian calendar dates, then we can use the Hebrew year that he identified for the start of the siege. Therefore, the start of the siege would be 10 Teveth 3173, 17 December 589 BC Julian, or Julian day 1506641.5.
End of 70 Years of Desolation
The period of desolation ended with the laying of the foundation of the 2 nd Temple. Chapter 2, verses 10 and 15-19 of Haggai explicitly states that the nation would be blessed from that date forward in comparison to what had happened previously—which is consistent with that date ending the period of desolation.
(ESV) Haggai 2:10 “On the twenty-fourth day of the ninth month, in the second year of Darius, the word of the LORD came by Haggai the prophet,
V. 15 “Now then, consider from this day onward.  Before stone was placed upon stone in the temple of the LORD,”
Or backward; also verse 18
16 how did you fare? When  one came to a heap of twenty measures, there were but ten. When one came to the wine vat to draw fifty measures, there were but twenty.
Probable reading (compare Septuagint); Hebrew Lord, since they were. When
17 I struck you and all the products of your toil with blight and with mildew and with hail, yet you did not turn to me, declares the LORD. 18 Consider from this day onward, from the twenty-fourth day of the ninth month. Since the day that the foundation of the LORD’s temple was laid, consider: 19 Is the seed yet in the barn? Indeed, the vine, the fig tree, the pomegranate, and the olive tree have yielded nothing. But from this day on I will bless you.”
Haggai recorded the date of the laying of the foundation as the 24th day of the ninth month of the second year of Darius. The 24th day of the ninth month would be 24 Kislev. Finegan, Handbook of Biblical Chronology, Revised Edition, page 267 dates the year as 520 BC. 24 Kislev of 520 BC corresponds to 24 Kislev 3242, 17 December 520 BC, or Julian date 1531843.5.
How Long is 70 years?
How long was the 70 years? You published a technique for determining the duration of prophecies in “Calculating Daniel’s Seventy Weeks Prophecy (Daniel 9:24-27) and the Length of the Tribulation Period” (https://biblicalreadercommunications.com/2019/04/23/calculating-daniels-seventy-weeks-prophecy-daniel-924-27-and-the-length-of-the-tribulation-period/).
Your technique for calculating durations of prophecies is as follows:
-Determine the number of prophetic years.
-Determine the number of prophetic days, which is (360 days per prophetic year) multiplied by the (number of prophetic years).
-The number of solar years is the integer number of (prophetic days/solar days per year).
-The number of days is the integer number of (solar years) multiplied by the (number of solar days per year).
Using this approach, then the analysis progresses as follows:
-The number of prophetic days is 360 days/prophetic year x 70 prophetic years = 25,200 prophetic days.
-The number of solar years would be 25,200 days/(365.24219 days/year), which equals 68.995315 years. Rounded, the number of solar years is 69 years.
-Thus, the number of days in the prophecy is 69 years * (365.24219 days/year) = 25,202 days.
As noted above, the starting point of the prophecy of the desolation is the start of the siege on 10 Teveth 3173, corresponding to Julian day 1506641.5 and 17 December 589 BC Julian.
Adding 25,202 days to Julian day 1506641.5 gives Julian day 1531843.5 for the predicted end point of the prophecy. That Julian day corresponds to 24 Kislev 3242 or 17 December 520 BC Julian, which is the ending point of the prophecy noted above. The predicted end date of the prophecy matches exactly the date that the foundation of the Second Temple was laid as recorded in Scripture.
Calendar Conversion Issues
My analysis is valid if Thiele is wrong, which he appears to be. I’ve checked about ten of the Julian dates in Thiele; all but one of the dates that I reviewed appear to be wrong. When the Julian dates that he provides are converted back into the Hebrew calendar, they generate month and day values which are inconsistent with the Scriptural citation on which they are based. The errors are of the magnitude of one month or less. The errors would appear to be consistent with a poor algorithm which was about a month in error. The preface of the first edition of his book was dated 1951 (page 18), which considerably predates simple computation of calendar conversions. Thiele’s analysis—at least in the 1983 revised edition—of the chronology of the reigns of the Old Testament kings of Israel and Judah is not based on the conversion of dates from the Hebrew calendar to the Julian calendar. Although he used Julian years, he used Hebrew months in his analysis. His focus was identifying how the regnal years were numbered and whether accession years were used. As far as I can tell, the Julian dates—as opposed to Julian years—included in the latter portion of the text do not factor into his analysis.
I’ve also checked—to the best of my ability—the online calendar converters. The one that I use is at https://www.fourmilab.ch/documents/calendar/ . I tested it against Wolfram Alpha and two other converters; they all give the same results for calendar conversions in this era. Since all four converters give the same results, that suggests either that they are all correct or all err identically.
If my analysis is correct, then the one of the proposed dates for the start of the siege of Jerusalem is in error by about a month. The correct date would be 17 December 589 BC, while Thiele argued for 15 January 588 BC. Moreover, Finegan’s Handbook of Biblical Chronology (page 259) is also wrong for this date; Finegan used the same date that Thiele used. If my analysis is correct, then why hasn’t anyone caught this error before now?
More importantly, we see again that a prophecy in Scripture is fulfilled to the exact day over a period of about 70 years.
Comments, suggestions, and critiques are welcomed.
Guest Writer & Friend of Sam A. Smith