Harappa is a city in Punjab, northeast Pakistan, located beside a former course of the Ravi River; about 35km southwest of Sahiwal.
 The earliest radiocarbon dating mentioned on the web is 2725+-185 BC (uncalibrated) or 3338, 3213, 3203 BC calibrated, giving a midpoint of 3251 BC. Maybe this comes from S.P.Gupta, 1993, "Longer chronology of the Indus-Saraswati Civilization", Puratattva, No. 23, 1992-93, pp. 21-29.  Mohan Jodaro is also same period city which is now in India Rajasthan.