A solstice happens at the same time for all of us. The sun has a very large significance to us both spiritually and physiologically. It is both helping us evolve spiritually as well as helping the human body run efficiently. The sun has a spiritual significance since the dawn of existence and many have documented this significance based on ancient texts and ancient structures erected to notify the people of  the changing of seasons. Ancient societies did not have calendars to track the seasons so these structures could have been built to signify the end of one season or solstice and the beginning of a new.