Please enter the date in year, month, day format only
*This is a c++ program which uses files to keep track on the events that are created, deleted
*This program always keep the record in sorted order and aso displays in sorted order
*We can perform various operations on calendar such as searching a month-wise calendar, day-wise calendar creating events, deleting events
*There is menu() function that performs almost all operations that can be performed on calendar which has choices of operations, such that selecting paticular choices performs particular operations
*menu() function runs infinitely and should be terminated only by the choice which has exit option.
*please exit by above option only
*Alternatively we can call display_year(), display_month(), display_day() for displaying the calendar and events by year, month, day respectively
*We can also cal set_event(), delete_event() functions for creating and deleting events respectively