That pale disc bouncing between the poles is polar day, where the sun never sets. The shadow sweeping in and out at the opposite pole is polar night, where the sun never rises. The Arctic Circle is defined by this phenomenon. It is the area where the sun won’t rise for at least 1 day a year.

This map shows the hour of sunrise globally through the year. It reveals time zones following national and, sometimes, regional boundaries, and slicing through the oceans.