If I recall correctly, all Maiar (of which sauron is one) were created by Eru before time was countable, i.e. “in the beginning”. Once valinor and the two trees were created, time was counted by “the years of the trees” which were each approximately 10 of our years, and several thousands passed before the end of the First Age (and then of course the second and third ages happened). I assume someone did the appropriate conversion and got the number from there. It seems reasonable to me.
Plus, once you’re old enough to pour your cruelty, malice, and will to dominate all life into some jewelry, you stop counting the years, don’t you?
If I recall correctly, all Maiar (of which sauron is one) were created by Eru before time was countable, i.e. “in the beginning”. Once valinor and the two trees were created, time was counted by “the years of the trees” which were each approximately 10 of our years, and several thousands passed before the end of the First Age (and then of course the second and third ages happened). I assume someone did the appropriate conversion and got the number from there. It seems reasonable to me.
Plus, once you’re old enough to pour your cruelty, malice, and will to dominate all life into some jewelry, you stop counting the years, don’t you?
Not to mention the 3500 Valian years (i.e. 35,000 normal years) that passed after the creation of Arda but before the years of the trees.
I don’t have a clu3 about LTR-lore but another nerd-comment:
As I understand our current understanding of time it is still not countable.