Careful questions to Jill and Dorcas, the answers of which he then related to what he had read, enabled him to grok in part enough to relieve his mind somewhat the city was very young; it had been founded only a little over two Earth centuries ago.  Since Earth time units had no real flavor for him, he converted to Martian years and Martian numbers years (3^4 + 3^3 = 108 Martian years).