Simplified Summary: "And it came to pass in the month Nisan..." (Neh. 2.1) starts off Nisan 1 in 444 B.C., the declaration of the building of the temple noted in Neh 2.8, "And a letter unto Asaph the keeper of the king's forest, that he may give me timber to make beams for the gates of the palace which [appertained] to the house, and for the wall of the city, and for the house that I shall enter into. And the king granted me, according to the good hand of my God upon me."  From this day to Nisan 10, 33 AD, March 30th, the day Jesus entered Jerusalem, is exactly 483 Biblical years = 30x12x483 =173,880 days. 483 years is used because that is number in Daniel's prophecy in 9.25, "seven weeks, and threescore and two weeks" (69x7). "After threescore and two weeks shall Messiah be cut off". This prophecy has been fulfilled because 444 BC Nisan 1 to Nisan 14, April 1 (Friday), 33 AD is more than 173,880 days and the 173,880 days extends beyond 30 AD.

 

---

 

The Times of Your Life - A solar year is actually 365.2475 days in the modern Gregorian calendar, but 365.25 days in the Julian calendar (because there is a leap year every 4 years) that would have been used during the 1st Century AD. The length of a Gregorian year is 365.2425 days (because there is a leap year every 4 years, but not in years ending in "00" unless the year is divisible by 400, when it is still a leap year). The Gregorian year is accurate to 1 day in 3000 years. For complete accuracy, we would need a calendar that averaged 365.24219879 days, because it takes the Earth 365.24219879 days to orbit the Sun (the so-clled "tropical year", i.e. the interval between two transits of the Sun through the equinoxes). Finally, just to confuse us all, there is also the "sidereal year" - 365.25636042 days - this is the interval for the Sun to return to the same point on the ecliptic (i.e. with the stars in the same positions above our heads). Added from Gary Turner: The gap of 25 days is less than a month, which, considering the modern Hebrew and Gregorian calendars can differ by this amount from year to year because of the different ways in which they work, and that Neh. 2:1 is actually quite vague about which day of the month of Nisan is being referred to, the fact that the prophecy is accurate to the month, not just the year, is quite amazing!

 

Gary Turner: The difference between the two Nissan 14 dates is that Nissan 14 was April 3st if you convert it to the Julian Calendar (which the Romans were using at the time) but April 1rd if you convert it to the Gregorian Calendar (which we use now, because it is more accurate).

Looking at the "decimal points" after the 365, let's take it from first principles:

The Julian calendar had a leap year every 4 years, which added exactly a quarter of a day, on average, to the length of the average year - so the Julian year was 365.25 days long.

The Gregorian Calendar has a leap year every 4 years if the year is not divisible by 100, but if it is divisible by 100, that year is NOT a leap year UNLESS it is also divisible by 400. This makes the length of the average Gregorian year 365 + (1/4) - (1/100) + (1/400) = 365.2425 days per year. Since this is the more accurate calculation, this is the one you should use over large stretches of time (such as 173, 880 days). However, remember the 2-day difference between the Gregorian and Julian calendars at this time - which gradually became larger over the centuries, hence the need to introduce the new calendar in the 16th Century).

This means that neither figure of 365.24 nor 365.2475 should be used, but 365.2425 instead. However, all of this is rather academic, since we are only using 173, 880 days as a calculation tool - I don't think Daniel's prophecy is claiming to be accurate to the exact day - after all, it's only saying that Jesus would be cut off after 483 "prophetic" years - so we can only expect accuracy to the correct year, not to the exact day.

As for finding a calendar to plug all this into, the Web site I originally used is now defunct, and others that I have come across only convert "modern" dates, so if you can find one out there that goes back to AD 1 or earlier, please let me know!

 

 

---

 

For additional details, I have organized this reasoning from the general to the specific, and it is an awesome proof (thanks to Glen Amyklein):

 

My footnotes to NLT:
Ezra 6:15 Aramaic on the third day of the month Adar, of the Hebrew calendar. This event occurred on March 12, 515 B.C.; also see note on 3:1. The temple was completed in 515 B.C.
6:19 Hebrew On the fourteenth day of the first month, of the Hebrew calendar. This event occurred on April 21, 515 B.C.; also see note on 3:1.zra 7.1 There is a gap of almost 60 years between the events of chapters 6 and 7. The story in the book of Esther occured during this time, in the reign of Xerxes, who ruled from 486-465 B.C. Artaxerxes, his son, became king in 465, and Ezra returned to Jerusalem in 458.
7.6 Eighty years after the first exhiles returned to Jerusalem (2.1), Ezra himself returned. This was his first trip, and it took four months. The Temple had been standing for about 58 years. Up to this point in the narrative, Ezra had remained in Babylon, probably compiling a record of events that taken place.
Why did he have to ask the king if he could return? Ezra wanted to lead many Jews back to Jerusalem, and he needed a decree from the king stating that any Jew who wanted to return could do so. This decree would be like a passport in case they ran into opposition along the way.
1.1 The book of Ezra opens in 538 BC, 48 years after Nebuchadneezer destroyed Jerusalem, defeated the southern kingdom of Judah, and carried the Jews away to Babylon as captives (2 Kings 25; 2 Chron 36). Nebuchadneezar died in 562, and because his successors were not strong, Babylon was overthrown by Persia in 539, just prior to the events recordered in Ezra. Both Babylon and Persia had relaxed policies towards captives, allowing them to return to their homes and take ordinary jobs.
1.1 Jeremaiah prophesied that the Jews would remain in captivity for 70 years (Jeremaiah 25.11, 29.10). The 70 year period has been calculated two different ways: (1) form the first captivity in 605 BC (2 Kings 24.1) until the altar was rebuilt by the by; the returning exiles in 537 (Ezra 3.1-6), or (2) from the detruction of the Temple in 586 until the exiles finished the rebuilding in 515. Many scholars prefer the second approach because the Temple was the focus and heartbeat of the nation. Without the Temple, the Jews did not consider themselves established as a nation.
1:1 The first year of Cyrus's reign was 538 B.C.
Neh. 2:1 Hebrew In the month of Nisan. This month of the Hebrew lunar calendar occurred in April and May 445 B.C.
Ezra 1:1 The first year of Cyrus's reign was 538 B.C.
7:1 Artaxerxes reigned 465–424 B.C.
7:1 Or descendant; see 1 Chr 6:14.
7:3 Or descendant; see 1 Chr 6:6-10.
7:8 Hebrew in the fifth month. This month of the Hebrew lunar calendar occurred in August and September 458 B.C.
7:9 Hebrew on the first day of the first month, of the Hebrew calendar. This event occurred on April 8, 458 B.C.; also see note on 3:1.
3.1 Hebrew - in the seventh month. The year is not specific, so it may have been during Cyrus's first year (538 BC) or second year (537 BC). The seventh month of the Hebrew lunar calendar occurred in Sept/Oct 538 BC and Oct/Nov 537 BC.
7:9 Hebrew on the first day of the fifth month, of the Hebrew calendar. This event occurred on August 4, 458 B.C.; also see note on 3:1.
7:12 The original text of 7:12-26 is in Aramaic.

 

These specific verses in Ezra 1, 6, 7 and Nehemiah 2 have associated with them specific dates in the Scriptures to events at 538 B.C, 515 B.C., 458 B.C. and 445 B.C.. We know that the key word found is in Daniel 9.26 is that the Messiah will be cut off "after" 62 weeks (see below), so that any date older than or on Nisan 1, 444 B.C. are what we are trying to locate according to the Word of God as the starting point for the 483 years (that is, 7 weeks plus 62 weeks, though the last 7 year last week of the 70 weeks were not subsequently fulfilled because to consummate the last week -the last seven - there has to be an end of sin, as would be seen at Christ's return when He returns on the mount of olives. Zec 14:4 "On that day his feet shall stand on the Mount of Olives." Daniel 9.24 "Seventy weeks are determined upon thy people and upon thy holy city, to finish the transgression, and to make an end of sins." The only date that is appropriate, therefore, is 445 B.C. (more exacting precise details below) in Neh. 2.1-8 for the date "going forth of the commandment to restore and to build Jerusalem unto the anointed one" (Dan. 9.25) because 173,880 (69x7x360) days prior to Christ being cut off at 33 A.D. on the cross takes us to a time that follows when the declaration is made prior, which is necessary for this to be a true fulfilling prophecy since a solar years is approximately 365.24 days; and 365.24x(445+33) = 174,585 days. As you can see, the declaration did indeed proceed and was longer than the time constraint minimally required set forth in Daniel 9.25 of 69 weeks. The declaration was made in Neh. 2.1-8, not found elsewhere, not in the event of 458 B.C. that proceeded by 13 years which was not to rebuild the temple. Neh. 2.8 says "And a letter unto Asaph the keeper of the king's forest, that he may give me timber to make beams for the gates of the palace which [appertained] to the house, and for the wall of the city, and for the house that I shall enter into. And the king granted me, according to the good hand of my God upon me."  Neither does the declaration in 538 B.C. suffice as "the declaration" at that time because the temple was completed afterwards at 515 B.C., 33 years after, not 49 years (seven 7's). So that leaves only one choice, 445 B.C.

Watchman Nee said in his studies on page 82-89, CFP, in book format of Aids to Revelation (72-73 computer format, CFP),