Originally posted by Emopanther:

I don't think he's talking about the Event. In the meadows, after defeating Bonemass, Skeletons 'do' spawn every night, usually in the same locations. They'll kill everything around them, which is annoying.

But yes, it's normal.

Yes, that includes the regular nightspawns which occur in the same locations which are actually wherever you may happen to be ;)
The night spawns are the dev's crafty reminder not to keep working through the night and to go to bed ;)