June 20 On leap years, this day usually marks the summer solstice in the northern hemisphere and the winter solstice in the southern hemisphere. June_20
June 21 On non-leap years, this day marks the summer solstice in the northern hemisphere and the winter solstice in the southern hemisphere, and this is the day of the year with the longest hours of daylight in the northern hemisphere and the shortest in the southern hemisphere. In astrology, it is the cusp line between Gemini and Cancer. June_21