Tolkien's final First Age timeline

[Aiwendil]

Originally Posted by Galin

Admittedly, I'm making a broader statement here about Tolkien's possible mindset in the later phases of his writing. We can't know, but what I'm suggesting is that by the time this idea (Feanor asking for Galadriel's hair) rolled into JRRT's mind, much of what he'd written nearly 10 years earlier could have been forgotten . . .

. . . or replaced with something simpler. And if so, when Tolkien wrote The Shibboleth of Feanor, can we even be certain he had not reverted to the old date of Galadriel's birth in the Annals of Aman and injected the new ratio. I agree it would undo much of what he thought 10 years before (if he even remembered it) and even 3 years before (if he remembered that), but for all we know, an older Tolkien might have undone certain things for simplicity, or undone certain things because he no longer had his old texts to hand in any case, and was "creating anew" so to speak.

In fact, we know that by about the time of the writing of "The Shibboleth of Feanor", Tolkien had either rejected or forgotten* much of what he had developed over the course of the many "Time and Ageing" texts of c. 1959, since in the two texts given in ch. XIX, "Elvish Life-Cycles", he presents a completely different approach to Elvish longevity in the form of cycles of renewal. On its own, this doesn't specifically invalidate the date he had arrived at for Galadriel's birth, but taken together with the new element of Galadriel's hair as inspiration for the Silmarils, it certainly suggests very strongly that Tolkien did not consider the final form of the c. 1959 chronology to be fixed or correct.

*It is fairly clear that in the writings from this time period, Tolkien had occasional lapses of memory. Nonetheless, I think it unlikely, given the amount of time he had evidently devoted ten years earlier to working out the details of Elvish growth and ageing, that this can be attributed simply to forgetfulness.