When a passport is renewed does the 10 yr. period start at the renewal app date or orig. expiration date?

My US passport expires in March 2009. If I submit a renewal application 9 months in advance of that date, as the US Gov't. recommends, does the 10 year period for my new passport start at the renewal application date or is the time added to the expiration date (March 2009) of my original passport?|||It will be based on the date when the renewal passport is issued. If they issue in October of 2008 then your passport will expire in October of 2018. It's good to keep in mind that many foreign countries require a passport to be valid for at least 6 months upon entry. That's why they suggest getting the renewal that far in advance.