No.
Number of leaves is usually granted by taking into consideration the bare minimum leaves stated by the shops and establishment act or factories act or other act suitable to the company.
Note that the maximum number of leaves granted by the company should be in compliance with such number.
Now say for ex, as per the act you are to give 21 leaves to your employees per annum. The year for this purpose is usually calender year (Jan-Dec)
Now if someone joins in the mid year, the eligible leaves for the person won't be 21 but will be on pro-rata basis.
i.e. 21/12 * (no. of months he'd serve in the year)
Hope this clarified your doubt.