Every person who is responsible for paying any income chargeable under the head "Salaries" shall deduct income-tax on the estimated income of the assessee under the head "Salaries" for the financial year 2012-13. The income-tax is required to be calculated on the basis of the rates given above subject to provisions of section 206AA of the Act and shall be deducted at the time of each payment.
Yes, Sec 192 says income tax is required to be deducted at the time of payment but please note TDS would be deducted as per the tax provision of related year.
In your case tax can be deducted in April but it would be deducted as per the provision applicable for previous year ended in March( because income related to previous year) and such TDS can be remitted by 7th of May