those are latitudes/temperate zones to opposing seasons each side of 0 prime latitude the equator three seasons working 9 times a year. 8 seasonal shifts between 2 solsticies and 2 equinoxes with tropics stayingthe same all 12 months 52 weeks a year regardless the year has 365 or 366 days in it. Remember why the 366 day was added to artificial time of 7 days a week.