As per my understanding
5 Years Continuous Service
You will get the gratuity only after the completion of 5 years in the service. Also, there should not be any break in the service. It must be continuous.
Note, the condition of 5 years service has a small relaxation. In the last year, mere service of 240 days would be considered as one year. Hence, You would be eligible for the gratuity after 4 years and 240 days of continuous service.
If are working in an organisation which works for 5 days in a week or less, mere 190 days would be counted as last one year. Therefore, in such case, you would be eligible for the gratuity after 4 years and 190 days.
Continuous service means uninterrupted service. But, it does include the interruption due to, leave, sickness or accident. The strike, lay-off, or a lockout is also not considered as an interruption. Indeed, any interruption which is not due to the fault of the employee, would not be counted. But, if you have taken a sabbatical or leave without pay, then your service would get interrupted.
I will share other judgement for reference
8th May 2019 From India, Pune