What is the actual method of calculation of leaves for an adult worker  15 days or 18 days as per Factories Act

Dear All,
Kindly suggest the method of calculation of earned leave as per Factories Act,1948 as per Sec.79.As per Sec.79, Every worker who has worked in a factory for a period of 240 days or more in a year is entitled to leaves with wages in the subsequent year at the rate of one (1) leave for every twenty (20) days of work performed by him during the previous year. 
If we consider Weekly Offs and Public Holidays then the total earned leave for an adult worker after completion of one year will be 18 days and in case if we don't consider weekly offs and Public holidays then the total accumulation of leaves will be 15.My query is which is the actual method of calculating the total number of leaves for an adult worker  15 days or 18 days. 

There are two parts, one, the eligibility part and the second is calculation of the number of leaves.

An employee becomes eligible for leave only if he had worked for 240 days in the preceding year( Year means calendar year, ie, January to December) and this 240 days shall include all paid days, ie, leave with pay days, holidays and weekly off days.

an employee joined during the preceding year, say, July, shall work for the number of days in proportion to 240 days or 120 days.

Now once an employee becomes eligible for leave, the calculation part comes. He will get leave at the rate of one day for every 20 days PHYSICALLY PRESENT. That means number of leave earned is calculated on the actual days worked.

For example, one employee had worked for 155 days in the year 2019. There were 52 off days and 13 holidays (festival and national holidays). he was under lay off for 5 days in 2019. He had met with an accident while on duty and had to take leave (medical or ESI) for 5 days. In addition to the medical leave (on the ground of accidents while on duty) he had taken 10 days paid leave during 2019. Now the total working days (paid days) inclusive of paid holidays, paid weekly off days, lay off days, medical leave and casual leave is 240 days. He is eligible or earned leave in 2020. His leave for the year 2020 will be calculated on the basis of one day for every 20 days physically worked, or 155/20 or 7.75 or 8 days. That means for eligibility all paid leave days and those unpaid leaves due to ESI leave having taken after he had met with an accident while on duty are taken as days worked but he will earn leave only for days actually worked.

Normally, in a year of 365 days, 52 days will be off days and there may be around 10 days holidays. Then an employee who rarely takes any leave can work for 303 days. Then the total leave that he may earn is 15 days. if permitted to work on all the days (which is of course illegal) then also the total leave may be 18.

Thank you Madhu sir for your valuable inputs. To calculate earned leaves we have to consider the actual days worked by an adult worker in the factory. I have seen many statutory consultants are calculating earned leaves by including Weekly offs and public holidays and are also including weekly offs and public holidays in calculating 240 working days.

For deciding eligibility take the PAID holidays, weekly off days, lave days and lay off days but exclude them to count the number of days earned. An employee who has not worked for 240 days including paid holidays etc in the preceding year will not be eligible for earned leave in the current year. Once an employee becomes eligible, the number of leaves that he earns will be based on his physical days present only.

Hello Sir, Can you explain here why 240 days are considered while calculating EL annually ? specific reason for 240 days only ?

240 days is the cut off point made in various labour Acts in India.