What is the actual time relationship between the Land and our Earth realities?

Question

In the book series The Chronicles of Thomas Covenant the Unbeliever, there is a clear time discrepancy between the Land's time and our Earth time.

The Land's moves a much faster pace relative to our Earth time.

Roughly, between the first and second time Covenant is called to the Land,

forty years have passed in the latter (The Illearth War, chapter 3 "The Summoning"), whereas our Earth time was roughly by my calculations from chapters 1 & 2 of the same book 38 days. That makes roughly 1.05 years per day (40 years / 38 days = 1.05), though the day count could be off slightly.

But there are other places of possible time correlation (specifically Book 3, The Power that Preserves) and the question here is whether (1) any book reveals the exact time relationship (whether by statement or more clearly correlated timing to calculate), or (2) any official statement from the author reveals his view of the time relationship?

Please note:

While Covenant in the first series is unclear whether the Land is merely a dream or not, that is made certain in later books.

So I expect an answer to not rely on the ambiguity of Covenant's viewpoint, but on the fact of what has been revealed about the Land that would indicate some fixed relation exists.

Answer 1

Thanks to Chris's comment that led to the interviews, of which I just now got around to exploring and found the answer (over a year later our time, or in terms of the Land, as this answer will show, about 435 years).

My initial calculations in the question concluded

1 day = 1.05 years

which appears essentially correct, as Donaldson affirms from 11/7/2004:

The time ratio (1 day in Covenant's "real world" = 1 year in the Land) was built into the story from the beginning because I needed to be able to preserve the emotional continuity of what was happening to Covenant while still allowing enough time in the Land for important changes to take place.

He also gives a rough calculation between the first and second series earlier that year (2/25/2004):

Ten years passed in the "real" world (3500+ years in the Land)

This matches to a statement made in The Wounded Land, the first book of The Second Chronicles of Thomas Covenant, page 81, when Covenant is talking to Avery and pondering the passage of time based on what he was told:

"Ten years in our world ... Time is different here. It's faster" ... The Despiser had said, For a score of centuries. For nearly as many centuries more. "If the ratio stays the same, we're talking about three or four thousand years."*

Assuming a couple of leap years, and for sake of argument an exact 10 year span on our earth for calculations, then

The 1 to 1 calculation is about 3,652 years passed in the Land, but a low end of 3,470 (for 9 1/2 years) to high end of 3,835 (for 10 1/2 years). My initial 1 to 1.05 for 10 years actually matches exactly the high end of 3,835. Any of these numbers qualifies as fitting Foul's "For a score of centuries. For nearly as many centuries more" statement, since a score (20) of centuries (100) = 2000 years + "nearly" as much again = under 4000 years.