Dear Keshav,
This is not according to any judgment only. The same is given in the act itself. Also there are a lot of judgments on the same not only one. This is simple interpretation of the provision. The logic behind this is given below please understand the same.
Section 4 (1) says about the eligibility for gratuity. The section is given below.
4. Payment of gratuity.—(1) Gratuity shall be payable to an employee on the termination of his employment after he has rendered continuous service for not less than five years,—
(a) on his superannuation, or
(b) on his retirement or resignation, or
(c) on his death or disablement due to accident or disease:
Provided that the completion of continuous service of five years shall not be necessary where the termination of the employment of any employee is due to death or disablement:
1[Provided further that in the case of death of the employee, gratuity payable to him shall be paid to his nominee or, if no nomination has been made, to his heirs, and where any such nominees or heirs is a minor, the share of such minor, shall be deposited with the controlling authority who shall invest the same for the benefit of such minor in such bank or other financial institution, as may be prescribed, until such minor attains majority.]
Now let us see the definition of one continuous year of service under section 2A
[2A. Continuous service.—For the purposes of this Act,—
(1) an employee shall be said to be in continuous service for a period if he has, for that period, been in uninterrupted service, including service which may be interrupted on account of sickness, accident, leave, absence from duty without leave (not being absence in respect of which an order 2[***] treating the absence as break in service has been passed in accordance with the standing orders, rules or regulations governing the employees of the establishment), lay-off, strike or a lock-out or cessation of work not due to any fault of the employee, whether such uninterrupted or interrupted service was rendered before or after the commencement of this Act;
(2) where an employee (not being an employee employed in a seasonal establishment) is not in continuous service within the meaning of clause (1), for any period of one year or six months, he shall be deemed to be in continuous service under the employer—
(a) for the said period of one year, if the employee during the period of twelve calendar months preceding the date with reference to which calculation is to be made, has actually worked under the employer for not less than—
(i) one hundred and ninety days, in the case of any employee employed below the ground in a mine or in an establish-ment which works for less than six days in a week; and
(ii) two hundred and forty days, in any other case;
Now in the light of the above provisions we can say that a person is eligible for Gratuity when he completes 4 year and 240 days in the fifth year.
Please revert in case of any further doubt.