Meteorological seasons are a convenience of months. Astronomical seasons begin at equinoxes and solstices. Cultural seasons are festivals: Nowruz, Songkran, Midsummer, the Ghost Festival, Inti Raymi, the harvest moons.
Climate is now moving the lived season away from the named one. Cherry blossom records in Kyoto, grape harvests in Burgundy, and ice-out on northern lakes are calendars that do not ask permission. Episode 9 treats those records as seriously as stone inscriptions.
This pillar is where the series stops being about clocks and becomes about whether a people can stay in rhythm with a changing Earth.