When was the Yin Yang symbol first used?

Question

How far back does the first recorded use of the yin yang symbol go back in history.

Answer 1

The origin of the symbol itself can be traced back to 1000 BCE. Depictions of Yin/Yang have been found on oracle bones (skeletons of animals used in Chinese ritual) dating from this era. It is also believed that the Yin/Yang symbol became widely used in Taoist temples (as they are today), during this time as well. The earliest textual evidence of Yin/Yang can be found in The Book of Songs written by Shijing. It is important to note however, that the origin of Yin/Yang is debatable. Evidence could still resurface, dating this symbol to an older time and era.

Answer 2

The Chinese Taiji symbol (Tai-Chi, or taijitu) predates the Song dynasty (960-1279).  Known in the West as the Yin-Yang symbol, it appears in the ancient I Ching (or YiJing, the "Book of Changes").  It is meant to depict the two traditional types of complementary principles from which all things are supposed to come from, Yin and Yang, whirling within an eternally turning circle representing the primordial void (the Tao). The Confucian Tai-Chi symbol represents actual plenitude, whereas the Taoist Wu-Chi symbol (an empty circle) symbolizes undifferentiated emptiness, but also the infinite potential of the primordial Tao...

Yin and Yang are each divided into greater and lesser "phases" (or "elements").  A fifth central phase (earth) represents a perfect transformation equilibrium.

The oldest known Tai-Chi symbol was carved in the stone of a Korean Buddhist temple in AD 682.  A stylized version of the Ying-Yang symbol (Eum-Yang to Koreans) appears on the modern [South] Korean Flag (T'aeGuk-Ki) which was first used in 1882, by the diplomat Young-Hyo Park on a mission to Japan.  The flag was banned during the Japanese occupation of Korea, from 1910 to 1945.