What time do libraries usually close in Finland ?
It depends on the library, its size, location and staff. Public libraries usually close in the evening at 7 or 8 pm.
In Helsinki City Library most of our libraries close at 8 pm. You could check the library opening hours here http://www.lib.hel.fi/en-GB/kirjastot/
Library 10 in the Helsinki city center closes at 10 pm.
From site Libraries.fi you can search for all libraries in Finland.