Confirmed via testing that moon phases are actually 1 below their listed value, as such 0 is full moon, when wikis show it as 1.

I don't really consider this a bug as it's like the internal values of the game, but given that when people look up moon phases they're likely to assume 1 in the wiki = 1 in the mod. It would probably be better to change the mod to accommodate that. Believe applying a -1 to any moon phase values added, would implement this behaviour.

Confirmed present in the 1.20.1 and 1.21.1 version.