Advance Tax 2nd Qtr

It is paid over total estimated tax payable upto 31st March.

i.e for 2nd quarter..... 

1. As per sec 207, it is the responsibility of the assessee to pay advance tax as per your estimated profit. The due date for the Q2 will be on or before and 45% of the tax liability should have been paid. 
2. The provision has not specified any such condition that profit should be at the end of the month. And it would be wise to take the profit as on 15th of September since 45% of tax liability will be calculated as on 15th September. 
3. Hence take P&L as on 15th of September and pay the advance tax liability. 
Please correct me if the above solution has an alternative view.