Some gather in my house,
because I am a part of a fad.

Sometimes I am dark.
and sometimes I am light.

I could be the savior at sunrise,
and sometimes the savior of night.

What am I?

its a good answer!

some people dont like trees because they need land or whatever. some people are tree huggers.

some people like treehouses because they are a fad during childhood. or CLUBS...fads

Trees can be dark OR light, think of the leaves

They can save you at sunrise or night, depending on what u need.