You don't need calendar for optics. You don't even need calendar for the UHV (conquer England, France and the Netherlands and then build a settler in an Aztec or Incan city). I killed Portugal without the "exploit", my cities were Santiago, Zaragoza and that city north of the clam in the south, Sevilla I believe. I also started to build Knights early, so conquering France was not that difficult, although they conquered Rome very early, so they had Pikemen and Knights. I can assure you that I haven't used the world builder. I actually lost some settlers and lots of workers to Dog Soldiers because I was too lazy to care about their safety, and yet I did not open the world builder. The reason why the terrain is so bright, is that I used the "view terrain" button to better show the difference between the borders. So, I did not use the world builder for any purposes in that game.
EDIT: Actually it's better to skip calendar until you've met China, Khmer and Japan. Don't trade a useful tech to the Europeans, buy them from the Khmer, the Aztec or the Inca.