There is indeed an adaptative difficulty called « Loop Stress », though it doesn't depend of the time of day nor does it reset each loop, it's global to the game.
Basically it starts already quite low and if you die or fail, it goes down and when you kill a visionary, complete a Lead stage, finish a complete loop, etc, it goes up. Once it's on max, NPCs are much more vicious in their aim, their fire rate, the
simultaneity of gunners, they have better loadout (health trinkets, anti-headshot, or weapons that drain you Power) and they react faster and investigate longer. You can be invaded up to 4 times a loop (0 when your Loop stress is too low). But NPC loot is better (cause they're better stuffed) and there are much more residuum nodes in the levels etc.
It never becomes extremely difficult (this is not the point of the game, it's a power fantasy) but it still gives some challenge and if you add Julianna invaders, it can become quite hard... So, don't really trust early game lets play, it becomes harder and, in my opinion, more fun on a challenge perspective on mid/late game.