I thought you might find this interesting. If Middle-earth can be dated and the end of the Fourth Age happened around 4008 BC then the First and Second Ages would correspond to a Golden and Silver Ages that started right about 10500 BC. Sound familiar? What did Tolkien know that he wasn't telling us?
WHEN DID THE FOURTH AGE BEGIN?
Middle-earth, as envisioned by J.R.R. Tolkien, was not some faraway planet as in a science fiction story but rather the very world we live in. The events portrayed in his fantasy novels, The Hobbit and The Lord of the Rings occured during an imaginary period in our past. But when?
While the chronology he presented in Appendix D of Return of the King is intricately detailed it contains no reference point so as to allow us to date it. It does make clear, however, that the usual laws of astronomy are valid, even going so far as to give the length of a tropical year down to the second.
So there remains the possibibility of determining what year some events occured by looking at the astronomical phenomenon that are predicted to have occured then and comparing them to what is described in the books. This has been used sucessfully to date many things in ancient times.
To start with we can use a quote from one of Tolkien's letters;
'I imagine the gap [between the Fall of Barad-dur and modern times] to be about 6000 years; that is we are now at the end of the Fifth Age, if the Ages were about the same length as the Second Age and the Third Age. But they have, I think, quickened; and I imagine we are actually at the end of the Sixth Age, or in the Seventh.'
Taken literally this gives us an upper and lower bound to the year 3019 of the Third Age and thus the key to the whole chronology. Since the letter was written in 1958 this would put it at 4043 BC, give or take 500 years. So we are left with choosing one from among a 1001 years, a seemingly impossible task.
But it is not as difficult as it looks. In The Fellowship of the Ring there is this line;
'The Moon, now at the full, rose over the mountains, and cast a pale light in which the shadows of stones were black.'
The chronology in the Appendix gives this date as January 8 of the Third Age in Shire Reckoning. But which day is that in a conventional calendar? In the Appendix he also states;
'It appears, however, that Mid-Year's Day was intended to correspond as nearly as possible to the summer solstices. In that case the Shire dates were actually in advance of ours by some ten days, and our New Year's Day corresponded more or less to the Shire January 9.'
Sounds simple, right? But this must not be referring to January 1 in a modern calendar now in use such as the Gregorian merely backdated 6,000 years. This is because the solstices occured on quite different days from that of the present. Six millenia ago the winter solstice was on about December 18 as opposed to December 22 today. In fact, there was a difference of 187 days between solstices then against 182 now. It may be that the Shire and other calendars were developed at the start of the Second Age and changed little since. The seasons 13,000 years ago were much closer to the way they are today due to a difference of half a 26,000 year precession cycle between our time and then. As an example, Christmas used to coincide with the winter solstice but is still celebrated on December 25 instead of the 22nd.
Thus we must be open to a number of different days with which to match to any particular one in the Shire calendar. But we can reasonably narrow it down to those that will not move the solstices too far from their rightful places on Yule and Mid-Year's Day.
I considered the Gregorian dates of December 26 to 29 to be acceptable choices for January 8 of the Shire. Then I listed all the years between 3543 and 4543 BC in which there was a full moon in the evening on one of those days. This reduced 1001 years to a little over 130.
Fortunately The Fellowship of the Ring also gives us some valuable information on the position and brightness of the planet Venus on the evening of February 15(S.R.) in these lines;
'The Evening Star had risen and was shining with white fire above the western woods.'
'Earendil, the Evening Star, most beloved of the Elves, shone clear above. So bright was it that the figure of the Elven-lady cast a dim shadow on the ground.'
This clearly indicates that Venus was both somewhat high above the horizon and near maximum brightness. This can only occur between the times of greatest elongation and greatest brilliancy of the planet in the night sky. This narrows down the possible years considerably. Only six good ones are left; 4000, 4008, 4016, 4494, 4502, and 4510 BC.
So far, so good. But which of the six years? The second triplet just barely fits within the definition of 'about 6,000' years ago whereas the first almost hit it on the nose. So I excluded the former.
This leaves the three years of 4000, 4008, and 4016 BC. The middle one gives dates for the solstices that are closer to the Yule and Mid-Year's Days as intended by the Shire calendar. So I chose 4008 BC as the most likely candidate for 3019 of the Third Age.
If this is, in fact, the correct year then January 8 in Shire Reckoning would be December 28, 4009 BC in the Gregorian or January 29, 4008 BC in the Julian calendar. The Fall of Barad-dur would thus have happened on March 15 or April 16, 4008 BC.