Mystery island spawning glitch?

[Runic Legend]

I got a bamboo forest island and arrived around 6:30, I set it up to try and increase tarantula spawns by cutting everything down, it is now 7:14 and the only thing spawning still is butterflies and locusts. Is mystery island spawned based on what time you arrive and not based on real time?

 

[Krissi2197]

It's based on when you arrive. I know this because I was on an island and put my switch into sleep mode and when I woke up the next morning, Tarantulas were still spawning.