There are four earth hours to the in-game day. Every game day, living NPCs of any race gain 1% health and damage. Every four days, at 6 am server time, new NPCs "spawn." Every day, trees "grow." wood volume increases 1% (visible over time). This makes for deep forests, far from cities, filled with massive, thick trees. Saplings also spawn at random every four days, along with angels and demons in their northern isles.