Strictly speaking, anything prior to about the 13th century BCE belongs to Chinese prehistory, as this is the earliest era for which we've discovered contemporary written materials. Written references to the Xia kingdom only appear a few centuries later, in the literary and historical texts of the Western Zhou period (c. 11th-8th centuries BCE). Which is to say, we only start to find references to the Xia state about 500 years after the supposed fall of the Xia. Consequently, historians and archaeologists outside of China tend to regard the Xia more as a piece of Zhou-era folklore than as a historical reality. They are more likely to refer to archaeological cultures from this era- Erlitou, Longshan, and the like- rather than to the supposed Xia.

In conclusion:

• The purported Xia period (23rd-18th centuries BCE, according to the traditional chronology established under the Han dynasty) corresponds to the late Neolithic and early Bronze Age in Central China; this era belongs firmly to prehistory, as there are no Chinese written materials until the 13th century BCE

• The Xia state is likely a product of myth and folklore, and may not necessarily correspond to any single, real Chinese state. For this reason, Xia is typically not used in modern periodizations of Chinese history or prehistory.