solstice

/ˈsɑlstɪs/
noun
  1. Either of the two times each year when the sun reaches its highest or lowest point in the sky at noon, marking the longest and shortest days.
    • The summer solstice is the longest day of the year.
    • We planned our trip to Stonehenge to coincide with the summer solstice.
    • Many cultures celebrate the winter solstice with festivals of light.