Normally, sixty days means two months. In most companies, they specifically mention in the appointment letter, exit policy, standing orders, or employee handbook about the notice period. Some companies specifically mention that the resigned employee is not eligible to avail any leave during the notice period. Even in exigencies, if the employee avails leave, they need to compensate by working for additional days. For example, if your notice period is 60 days and you took 7 days of leave, with or without pay, then you would need to work for 7 more days.
In general, these 60/90 days are continuous, including the weekly off/holidays falling in between, almost a 2/3-month process but not actual working days.
Thanks and regards,
Kameswararao