June 21 is the longest day of the year for those living in the Northern hemisphere. What is the shortest day of the year for those living in the Southern hemisphere?

The Earth's axial tilt causes seasons to be reversed between the Northern and Southern Hemispheres. On June 21, the Northern Hemisphere is tilted toward the Sun, experiencing its summer solstice and longest day [1]. Conversely, on this same date, the Southern Hemisphere is tilted away from the Sun, marking its winter solstice [t1][t2]. Consequently, June 21 is the shortest day of the year for those living in the Southern Hemisphere [t10]. While December 21 is the shortest day for the Northern Hemisphere, it is the longest day (summer solstice) for the Southern Hemisphere [c2][t5]. Equinoxes on March 21 and September 23 result in nearly equal day and night globally [c3]. Therefore, the date that serves as the longest day in the north is simultaneously the shortest day in the south [c5][t6].

Sources

1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 12: Earth, Moon, and the Sun > 12.2.2 Seasons on the Earth > p. 179