What Time is considered "Night-time" (TS4:Vampires)

I've been running into weird occurances in the Vampires game pack when past 6 PM my vampiric energy drains as if they were in sunlight - and I was wondering if there was some specific time beyond what counts for the "Night owl' Trait (e.g. 6PM - 6AM) that Vampires have to adhere to...Also is it normal for the humor and hijinxs festival to drain this way even AFTER the sun sets on that given day? I nearly roast my only "good" vamp after waiting till 7 PM (their energy bar drained /excessively/ fast even under Dark Meditation; Eventually I cut the event short and headed home for fear the sunburn system was acting up.)