Dear Vinod,
Why you worry so much for the date. To get gratuity amount of Rs. 20 lakhs one has to have Rs. 1 lakh Basic salary and 35 years of continuous service.
Earlier gratuity amount upto Rs.10 lakhs was exempted under the Income Tax Act, which is enhanced now to Rs.20 lakhs. Besides the ceiling is also raised to Rs.20 lakhs.
Moreover, no law stops you to pay gratuity more than the ceiling amount, only the receiver is liable to pay income tax over and above the ceiling amount.
Suresh