Introduction We are all Africans. Local availability of food likely caused the first Homo sapiens to migrate out of Africa some 50,000-70,000 years ago and populate the rest of the world. Throughout human history, our behavior has been governed by our planet’s rotation and revolution around the sun, particularly from the time of the agricultural revolution about 12,000 years ago when the first calendars start to appear, guiding agricultural activities. In the modern age of globalization, however, food supply is relatively stable over the course of the year in many countries but the need for primary food production, local weather conditions and availability of daylight continue to impact activity of populations around the globe to varying degrees.