This would bring a more roguelike-ish experience, like for example the Malfunctions mod allows the player to set a specific amount of days after which a certain malfunction becomes enabled.
Like for example, the bracken would begin spawning after the 2nd day had passed, the jester after the 6th...
Would make the early game easier and potentially late-game more difficult if the mod could also change the chance of certain spawns. 
#Certain monsters can spawn after a set amount of days
bright crane
silent acornBOT
This would bring a more roguelike-ish experience, like for example the Malfuncti...
covert patrol
I had an idea like this but for weathers