Arithmetics on calendar dates in C or C++ (add N days to given date)

Question

I have been given a date, Which I am taking as an input like (day, month, year): 12, 03, 87.

Now I need to find out the date after n days.<

Answer 1

the easiest trick is to use time_t type and corresponding functions.

mktime will convert tm structure to time_t. which is an integer value counting the seconds starting 01-Jan-1970.

After you have a time_t value just add the seconds count you need (86400 per day).

To convert back, use gmtime or localtime