The Age of Surak was a time period that was witnessed by the Vulcan race. In an alternate timeline where the Terra Prime movement prevented the United Earth from joining the Coalition of Planets, T'Pol encountered a Romulan agent who looked appearanced as Vulcan ambassador Sarek. She concluded that the Romulans were the dissident Vulcan's who left their homeworld during the Age of Surak at the Time of the Sundering. (TOS novel: A Less Perfect Union) Presumably, the Age of Surak was when Surak spread his teachings of Logic throughout the planet.