Dev on the Paradox forums indicates their priority in developing new start dates : r/CrusaderKings

CK3 Dev Diary #37 - Making Mods, Page 10

Crusader Kings 3 Dev Diary #30 - Event Scripting, Page 3

Europa Universalis IV - Development Diary 12th of July 2022

Collections: Teaching Paradox, Crusader Kings III, Part III: Constructivisting a Kingdom – A Collection of Unmitigated Pedantry

Collections: Teaching Paradox, Crusader Kings III, Part III: Constructivisting a Kingdom – A Collection of Unmitigated Pedantry

Dev Diary #122: Regencies and Elegance of the Empire

Crusader Kings 3 Dev Diary #30 - Event Scripting, Page 3

CK3 Dev Diary #36 - Gotta Go Fast

Collections: Teaching Paradox, Crusader Kings III, Part III: Constructivisting a Kingdom – A Collection of Unmitigated Pedantry

Beginner's guide - Hearts of Iron 4 Wiki