As a vampire and assassin, darkness and night are like brother and sister to me. Within their cold embrace, I am best able to perform murderous and otherwise illicit deeds undetected. 19:00 (7:00 PM) is when night time begins for the purpose of my vampiric weakness to sunlight, and it ends at 05:00. However, it seems that 19:00 is not the darkest time of the day for the purpose of other entities seeing me. Or is it that despite the subtle changes in light, the game treats player-character visibility between 19:00 and 05:00 as the same, and the difference in darkness is either aesthetic or subjective?