What is the shortest day in a year?

The shortest day in a year is the winter solstice.

On the day of winter solstice, the sun moves to 270 degrees of the yellow meridian (winter solstice), and the position of the sun directly on the ground reaches the southernmost point of the year. The sun is almost direct to the Tropic of Capricorn (also known as the winter solstice daily line), and the sun is most biased towards the northern hemisphere. Therefore, in all parts of the northern hemisphere, the winter solstice is the shortest day in a year, and the farther north, the shorter the day.

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The longest day of the year:

On the day of summer solstice, the sun moves to 90 degrees of the yellow meridian (summer solstice, currently in Gemini), and the position where the sun directly hits the ground reaches the northernmost point of the year, almost directly to the Tropic of Cancer. At this time, the daylight hours in all parts of the northern hemisphere reach the longest in the whole year. For the Tropic of Cancer and its northern area, the summer solstice is also the highest day of the year at noon. On this day, the northern hemisphere received the most solar radiation, almost twice as much as the southern hemisphere.

The solstice in summer is the turning point of the sun. After this day, I went back. The direct sunlight point moved southward from the Tropic of Cancer, and the daylight in the northern hemisphere became shorter and shorter day by day. After the summer solstice, the Tropic of Cancer and its northern region, the midday sun altitude angle also began to decrease. At the same time, after the arrival of the summer solstice, the stars in the night sky gradually became summer stars.

Baidu encyclopedia-winter solstice