The company would decide the date for issuing the IPO after consulting with thier lead managers and registrars for the perfect date.
No one person decides the date as to when the IPO would be issued. However, when the SEBI clears the final draft prospectus of the IPO, it must be approved by the stock exchanges. After all of this is done, the company going public would have to decide when the date and duration should be fixed. Its where the company would discuss the perfect date with the lead managers, registrars to finalize the date and submit the proposal to the SEBI and stock exchange to issue the IPO.