Variations in the length of daytime and nighttime from season to season are due to

Variations in the length of daytime and nighttime from season to season are primarily caused by the revolution of the Earth around the Sun on a tilted axis [4]. The Earth's axis is inclined at an angle of 66.5 degrees to the plane of the ecliptic (or 23.5 degrees from the perpendicular) [1]. This fixed tilt, combined with the Earth's orbital motion, means that different hemispheres are tilted toward or away from the Sun at different times of the year [3]. When a hemisphere is tilted toward the Sun, it experiences longer daylight hours (summer), while the hemisphere tilted away experiences shorter days (winter). While the Earth's rotation creates the basic 24-hour day-night cycle, it is the interaction between the axial tilt and the revolution that drives the seasonal variation in day length [2].

Sources

1. [1] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 2: The Earth's Crust > The Earth's Revolution > p. 6
2. [4] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 19: The Motions of The Earth and Their Effects > Lunar Nodal Cycle > p. 266
3. [3] Science-Class VII . NCERT(Revised ed 2025) > Chapter 12: Earth, Moon, and the Sun > 12.2.2 Seasons on the Earth > p. 177
4. [2] Science-Class VII . NCERT(Revised ed 2025) > Chapter 12: Earth, Moon, and the Sun > In a Nutshell > p. 184