Dear Dr. Venkatraman,
Below are some examples of how priority date is determined.
Section 11(2): The example you have mentioned in your reply above holds true in this case.
Section 11(3): You have two provisionals, A dated 28/12/2009 and B dated 29/12/2009, your complete specification claims priority from both. Claim 1 is based on A then its priority date is 28/12/2009. Claim 2 is based on both A and B, its priority date is still 28/12/2009. Claim 3 is based on B only, its priority date is 29/12/2009
Section 11(4): Provisional filed 28/12/2009, complete filed with claim 1-5 on 26/12/2010, Claim 3-5 divided by way of a divisional dated 20/05/2011. Priority date for claims 3-5 remains 28/12/2009.
Section 11(5): An application, say a convention application, claims two priorities dated 28/12/2009 and 29/12/2009, for all purposes, the priority date of the claims would be earliest date i.e. 28/12/2009.
Section 11(6): If no other subsection applies, i.e. a direct complete specification has been filed then its filing date will be the priority date of the application.
Hope this helps.
Registered Patent Agent