regarding expirty date of H1b

[aspiringrak]

Hi,

I have got H1B approval in the month of July 2006(I797), But i didn't went to us consulate for visa stamping, if i go and get the h1b visa stamp now say Jun 2007 how long can i work in U.S.

Assuming i am entering the U.S Port on August 2007, What will be validity period the immigration officials will be issuing on the I94.

Basically i am trying to find out the whether h1b period i.e 3 years count starts on
1) Pettition approval date (in my case July 2006) or
2) Date on which the H1b visa has been stamped(in my case Jun 2007). or
3) Date on which i enter the US(In my case August 2007)

Thanks in advance

rakesh