Question

How would one go about calculating a date from a day-number in C++? I don’t require you to write the whole code, I just can’t figure out the maths to calculate the month and the day-of-month!

Example:

input: 1
output: 01/01/2012

input: 10
output: 01/10/2012

input: 365
output: 12/31/2012

It would always use the current year, if they exceeded 365, I would return 0. There is no need for a leap-year detection.

Answer 1

Use a date calc library as e.g. the fine Boost Date_Time library with which this becomes

using namespace boost::gregorian;
date d(2012,Jan,1);                     // or one of the other constructors
date d2 = d + days(365);                // or your other offsets