Do I need to apply sunscreen even indoors?

I don't tend to go out often.

I get a lot of blemishes on my skin.

I always make sure to apply it when I go out.

Then, I am wondering if I need to make sure to apply it even indoors.

If you need to apply it indoors

It means you have to apply it all day long,

I am also wondering if I need to keep applying it.