LOL Animals eat when they are hungry, they drink when they feel thirsty, so is there a particular time period for coitus? Generally unscheduled eating,drinking,sex habits might be found in cities than in villages.
I think evolution is the cause for such a major changes in human beings. Like for a 3rd world countries to run they brings in investments from different geographical locations, which need manpower support during their day timings (Eg: People in Indian work midnight shift to support US clients).
Apart from this, in order to meet targets Local companies keep changing shifts like Morning, Afternoon,Midnight..etc. Hospital nurses,doctors,cleaners also 24/7. These days even real estate people making workers work 24/7. So there is no fixed clock for internal organs. Hope someone could put up few points on how to deal with such situations which could be helpful to someone who is living such life.