What is the maximum length of a day on the poles?

At the poles, the sun remains above the horizon for approximately 6 months during summer and below the horizon for 6 months during winter. This occurs because of Earth's axial tilt (23.5°). At the North Pole, the sun is continuously above the horizon from the spring equinox to the autumn equinox. Similarly, at the South Pole, this occurs from the autumn equinox to the spring equinox. Therefore, the maximum length of a day at the poles is 6 months.