Every world clock I've used is a table. You read "Tokyo +9, São Paulo −3" and you still don't feel who's asleep. I wanted the opposite: look at the Earth, see the daylight band, and know instantly whether it's a reasonable hour to ping someone. That became Timetate — a world clock and meeting planner where the main interface is a 3D globe with a day/night terminator that tracks the real sun. This post is about the part people ask about: how the terminator is drawn, and why the naive ve...