All day at Arctic latitudes, and that assumes your skin is somewhat lightly pigmented, and that you don't live too far north. If you do, there is no sunlight du

All day at Arctic latitudes, and that assumes your skin is somewhat lightly pigmented, and that you don't live too far north. If you do, there is no sunlight during winter. If you've got a daytime job, live above the Arctic circle or immigrated, then your only option is to eat vitamin D-rich foods or eat supplements.