Stephen Poltz

the first big section describes time differences between the Valar (gods) , the Quando ( Rlves), and humans. Elves live longer because their "year" is comprised of multiple sun years. The live to be 100-200 in Elf years, but that's thousands in sun years. Then Tolkien goes on to calculate the major characters in each age and readjust their ages against the events of each Age. He has tons of calculations for the generations of elves from their awakening and later discovery by Olome Through the Great March to Valinor. He discusses rates of growth, puberty serial maturity number of children through the Ages, and the slowing down of aging and increase of spiritual development.