This little animation shows a point light inside a sun sphere, going around the circle of the Flat Earth Azimuthal Equidistant (United Nations) map. In it, we can see how night and day (and timezones) are still possible. I did not include the moon in this model, but it would essentially follow a similar path, giving less light and moving at a different pace. From what I understand about the Flat Earther's perspective, the sun and moon will also deviate in their path for the different seasons. The Book of Enoch gives us tremendous detail explaining the course of the luminaries that rule the day and the night.