H1 Extention (after six years)

Hi friends,

I have one question about H1-b extention after six years. I had my first three years H1-B visa starting on 01/01/2001-01/01/2004. then I got my second extention dated on 01/01/2004/-01/01/2007. During my second three years period, I had changed my job to another company and had my h1-b transfer done. This time I got my H1B valid date until 04/30/2007. Now I need to apply for the h1 extention for another 3 years since my I140 has been approved. The question is which date I need to put as the new H1-B visa starting date, 01/01/2007 or 04/30/2007?

Thank you for responses first.