Board Thread:General Mod Discussion/@comment-25565811-20170120101550/@comment-26172435-20170120104537

Note that minecraft does have an internal 'calendar' mechanism including a lunar cycle, as can be seen from the appearance of the moon at night. Mevans just needed a hookup to that cycle to add a modifier that affects the effective chance of an invasion spawning. I guess he did that. A bit of googling on minecraft functions will possibly provide info on the identity of the involved code part(s) and show whether it is used in mentioned LOTRmod class.