It helps to have some dates in mind, but dates are arbitrary. Dating by decades is at least convenient, however, starting with our own and looking backward. Also helpful is the Bible's generational calculus. There too we find ``generations,'' the generation of the flood, as the Rabbis put it, or the generation of the dispersion, meaning those who lived at history's putative beginning, touched forever after by their failure to erect a Tower of Babel. Assume that both are myths; there never was a Noah (though there may have been a flood), and there is no Tower of Babel.