At this time the northern hemisphere receives the greatest sunshine and the climate is at its hottest. On the winter solstice, sunlight strikes directly all the way down in the southern hemisphere, and the northern hemisphere is at its coldest. To tell the time in harmony with the rhythm of the seasons, one must calculate by the sun.
夏至時太陽直射北回歸線，這時北半球日照最足、氣候炎熱；冬至時太陽遠在南半球，北半球則陷入寒冬。