Game concept · All Under Heaven
Dynastic Cycle Era Type
The game also links it as Era Types.
From the game's encyclopedia
There are three Era Types in the Dynastic Cycle, they categorize the Dynastic Cycle Eras and place each into the three-part repeating nature of the Dynastic Cycle.
Era Types: Stable Era, Unstable Era, Chaotic Era
The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.
Dynastic Cycle Era Type is an entry of Crusader Kings III's in-game encyclopedia (All Under Heaven). The game explains it: "There are three Era Types in the Dynastic Cycle, they categorize the Dynastic Cycle Eras and place each into the three-part repeating nature of the Dynastic Cycle." It is part of Dynastic Cycle. The game also links it as Era Types. Patch 1.20.1.2, from game/common/game_concepts/tgp_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/tgp_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.