Generally speaking, the summer solstice occurs between June 21st and 22nd in the Gregorian calendar every year. When the sun moves to 90 degrees longitude, it is the node of the summer solstice, so the time of the summer solstice is not fixed. On this day in summer, the sun shines directly on the Tropic of Cancer. At this time, the northern hemisphere has the longest daylight hours of the year. After the summer solstice, the direct sunlight point gradually moves southward. Daylight time in the Northern Hemisphere begins at 05:43:33 on June 21, 2020. Lunar calendar: June 21 or April 22 (big) thirty years, which is the summer solstice. On this day in summer, the sun reaches the northernmost position of the year, almost hitting the Tropic of Cancer (23° 26′28″44 north latitude), and the northern hemisphere has the longest day.