Sunset is the moment the sun's upper edge sinks below a flat horizon; Sol calls the colour that follows, city by city, each evening.

The time follows from latitude, longitude and the date alone, and Sol computes it the same way for every instrument. The colour depends on cloud along the light's path to the west and the air between, which is why Sol calls it from a forecast, issues the call at least an hour before, and keeps every call to be checked later.

The time is geometry, exact years ahead; the colour is weather, known about two days out.