Dates in history usually count as before the birth of Jesus of Christ (Before Christ, BC) or from the year Jesus was born (Anno Domini, or AD. BC dates are counted backward, for instance the Indus Valley Civilization started around 3500 BC, but ended around 1500 BC. This may sound strange, but make sense if someone understands that it only means that this Indus Valley Civilization started 3500 years before Christ (BC), and ended two thousand years later, just 1500 years before him.
