99 Nights in the Forest Event Timers

Every 20 minutes. Wiki: "The Stronghold resets every 20 minutes and becomes harder each time, offering repeat opportunities for those prepared to face the challenge." — https://99-nights-in-the-forest.fandom.com/wiki/Cultist_Stronghold

Cultists raid your campfire on the fourth night and roughly every four nights after that — about every 20 minutes of real time, with more and stronger cultists each wave (up to eight). It is tied to your run, not to a server-wide clock, so there is no global countdown.

No fixed schedule.

Each day lasts 3 minutes and each night 1 minute 30 seconds — a 4½-minute cycle. It runs per-run rather than on a shared clock, so there is no global countdown: watch the Sun Dial in-game and be inside the firelight before it hits zero.

No fixed schedule.

No fixed schedule — this one is chance-based, so there is no countdown. Wiki: "The North Pole Biome has a 100% chance to spawn during Christmas, 0% during most of the year." — https://99-nights-in-the-forest.fandom.com/wiki/Biomes

No fixed schedule.