What year would they be born in?

[Mirage]

I think that would be silly, as that makes for ridiculously short intervals. The calm comes rather often if you look at the big picture. Braska's calm was about 10 years ago, right?

Yeah but this is the ultimate calm. Sin's dead forever now.

Then how would they do it prior to the eternal calm, which is when they were born?

Using Earth years make no sense, as we're not on Earth.