A moment in the year, as SeasonCycle.evaluate reports it.
Phase 0–1 (0 = midwinter, 0.5 = midsummer).
0 in high summer → 1 at the depth of winter.
0 while the year cools → 1 while it warms. See seasonWarming.
Nearest named season, for HUDs.
Whole years elapsed since construction.
A moment in the year, as SeasonCycle.evaluate reports it.