solstitial

/sɑlˈstɪʃəl/
adjective
  1. Relating to or happening at the time of the summer or winter solstice (the longest and shortest days of the year).
    • The solstitial point marks the sun's farthest position north or south of the equator.
    • The ancient monument was built to align with the solstitial sunrise.
    • Many cultures hold solstitial festivals to celebrate the changing seasons.