how many days of darkness

I wondered, when I entered this old prison bowling alley, how many days it had been completely dark and silent. No one had disturbed it for years. The flashlights that I used for light painting were the only sources of illumination that had been there for some time, and in all likelihood it will remain enveloped in nothingness for months or even years to come.

'how many days of darkness' taken in prison bowling alley.