Nocturnal Mobs

Mobs only spawn at night, and "despawn" at day.
You also get a few seconds of darkness at when night starts and a few seconds of night vision when daytime starts, so you can keep track of the time even while caving without a clock.

It will only despawn entities that:

• Are in the nocturnalmobs:hostiles tag
• Are in the overworld
• Do not have the {PersistenceRequired:1b} nbt (this includes mobs with nametags and those that have picked up items)
• Are not mounting an entity (careful with chicken jokeys!)

By default, the mobs in the nocturnalmobs:hostiles tag are:

• zombies
• zombie villagers
• husks
• drowneds
• skeletons
• strays
• spiders
• cave spiders
• creepers
• endermans
• phantoms
• slimes
• witches
  other mobs must be added via datapacks

You may disable the darkness and night vision by executing these commands:

• /function nocturnalmobs:config/disable_night_alert
• /function nocturnalmobs:config/disable_day_alert

and re-enable them using:

• /function nocturnalmobs:config/enable_night_alert
• /function nocturnalmobs:config/enable_day_alert