There are 3 cycles important for determining seasons, extreme temperatures, and length for any given planet in any given orbit as long as it isn't too elliptical. Those are: Orbital precession(this is what causes supermoons(when perigee lines up with a full moon)) Axial tilt(this determines the extremes of seasons and whether or not there are seasons) Axial precession(change in axial tilt over thousands of years) Eccentricity is important but only in the case of the orbit being so elliptical it actually changes zones as it orbits. For example, if eccentricity is close to 1, Summer would correspond to being in the hot zone and would be very short, Winter would correspond to being in the cold zone and would be very long(like maybe hundreds or thousands of years long. Spring and Fall would correspond to being in the habitable zone and have a length in between that of Summer and that of Winter. But assuming eccentricity is only a factor in that it determines orbital precession and is not so high that the planet is in different zones at different points in its orbit, how would I calculate the orbital precession and the axial precession of any planet around any star where the planet's eccentricity is not too extreme?