By 330 BCE or so, it was held as true in the Hellenistic world, and started spreading from there. That being said, some there still disbelieved and held other ideas to be likely. By the first century CE, Pliny the elder made the claim that it was completely agreed that the earth was spherical, and that the only areas of dispute were in the details, how the ocean could be curved, and on the nature of the antipodes. He also thought the earth might be shaped like a pine-cone. While some early Christian thinkers disputed the habitability of the underside of the sphere, most agreed that the earth was spherical. The uneducated through the middle ages believed the planet was round instead of spherical, but the more educated people knew. The Islamic world figured it out in the 9th century. China only got it in the 17th from the Jesuits.