05 June 2011
Contact your Dmat a/c agency. They will give a form for dematerialisation of securities which will have to be filled by you and submitted to the agency with physical shares. Your shares will be dematerialised in few days.
Date of dmat does not affect the status of long term holding of shares. In your case sale of shares within one month of transfer to dmat a/c will also result in long term capital gain.