> In San Francisco financial district it gets dark around 4pm in summer when sunset is around 9pm. No it doesn't, the ambient light is sufficient to allow norm

> In San Francisco financial district it gets dark around 4pm in summer when sunset is around 9pm. No it doesn't, the ambient light is sufficient to allow normal activities without requiring additional illumination until well past the summer solstice's dusk at 8:30pm. Unless by 'dark' you mean "I couldn't see the sun when I left to get a MUNI".