The longest day of the year occurs on the Summer Solstice (or Midsummer), typically on June 21st. Midnight Sun (or polar day) is the phenomenon when daytime lasts longer than 24 hours. In the Northern Hemisphere, this event occurs in the Arctic region (66.5°N) because of Earth’s 23.5-degree tilt, pointing the region toward the sun during its Summer orbit. The terminator line, which marks the boundary between day and night, falls short of the Arctic Circle on or around the Summer Solstice. Most locations in the Arctic experience at least a month or more of polar days. Due to atmospheric refraction, the Midnight Sun can be seen just south of the Arctic Circle, around 65.7°N.