Area Bosses - Which is which and how to find them

As you may notice since you commonly hunt Snowman, but he doesn't have a spawn notice when he appears. Not coincidentally, his spawn timer is in the data - 15 minutes. However, like with other free spawning bosses such as Pianus and Mushmom, there's a slight variance with him. Because his timer's so short, though, it means his spawn timer doesn't vary as wildly as others.

Is it possible to find a % variance then apply it to other bosses?

For example, if a 15 minute timer means it can spawn anywhere from 13.5 to 16.5 minutes, then it's 10%. Then apply it to BMM, which spawns around 48 hours and you'll get around 43.2 hours to 52.8 hours to spawn...

:f6:

Also, if his spawn timer is in the data, why can't you find the spawn timer for other bosses?