The yin yang symbol are over a thousand years old, It was first developed by Chinese scholars as a way to observe the sun's movement and to understand the universe.
They measured the length of shadows cast by the sun by putting a pole in the ground, In this way they were able to chart the number of days in a year.
The symbol comes from the dark and light areas represented by the movements of the sun and moon. Summer solstice is considered the birth of the yin cycle, and winter solstice is the birth of yang.