Project Duration

Hi, if a project has cash outflows in year 0, and year 1. Moving positive in year 2.

do we still calculate duration the same way ie PV of each cash flow * year

Then the sum of these divided by the sum of PVs? Or do we have to do something different due to the 1st year cash outflow? perhaps duration for when cash flows in + 1 year for outflow?

Thanks