Apply persisted Age celestial timing

docs/PORTING.md

@@ -291,6 +291,14 @@ Always, Cloudy, Rain, and Snow maintain non-thundering precipitation; Storm
 maintains rain and thunder. Minecraft still chooses rain versus snow from biome
 temperature, so dedicated Snow/Rain biome overrides remain future work.
 
+Version 0.2.20.0 applies persisted celestial timing to each Age. The saved
+period controls NeoForge's per-dimension clock rate, with a period of 1 matching
+a vanilla 20-minute day, 0.2 running five times faster, and 2 running at half
+speed. The saved phase sets the clock only during first-spawn initialization;
+later loads continue from saved world time. Celestial angle remains persisted
+for a future custom sky renderer because vanilla dimension data cannot rotate
+the sun's render plane.
+
 Version 0.2.14.0 restores the legacy Linking and Descriptive Book artwork for
 inventory items and gives each book its matching open-book texture when placed
 on a Book Stand. Return Linking Books created inside another Age also retain and