write new cosmology seasons

The old cycle of 12 seasons - Minquesta, Ohta, et c., came from a
solar-system model which had some problems.  The new one should be
faithful to how a roughly Earth-sized moon revolves around a Sun.

In the new model, Fenestra travels around the Ainumar every 60 days.
Each revolution is a 'cycle', and six cycles makes a year.