The following code example is taken from the book
The C++ Standard Library - A Tutorial and Reference, 2nd Edition
by Nicolai M. Josuttis, Addison Wesley Longman, 2012
Copyright © 2012 by Pearson Education, Inc. and Nicolai M. Josuttis
#include <chrono>
#include <ctime>
#include <iostream>
#include <string>
using namespace std;
string asString (const chrono::system_clock::time_point& tp)
{
time_t t = chrono::system_clock::to_time_t(tp); // convert to system time
string ts = ctime(&t); // convert to calendar time
ts.resize(ts.size()-1); // skip trailing newline
return ts;
}
int main()
{
// define type for durations that represent day(s):
typedef chrono::duration<int,ratio<3600*24>> Days;
// process the epoch of this system clock
chrono::time_point<chrono::system_clock> tp;
cout << "epoch: " << asString(tp) << endl;
// add one day, 23 hours, and 55 minutes
tp += Days(1) + chrono::hours(23) + chrono::minutes(55);
cout << "later: " << asString(tp) << endl;
// process difference from epoch in minutes and days:
auto diff = tp - chrono::system_clock::time_point();
cout << "diff: "
<< chrono::duration_cast<chrono::minutes>(diff).count()
<< " minute(s)" << endl;
Days days = chrono::duration_cast<Days>(diff);
cout << "diff: " << days.count() << " day(s)" << endl;
// subtract one year (hoping it is valid and not a leap year)
tp -= chrono::hours(24*365);
cout << "-1 year: " << asString(tp) << endl;
// subtract 50 years (hoping it is valid and ignoring leap years)
tp -= chrono::duration<int,ratio<3600*24*365>>(50);
cout << "-50 years: " << asString(tp) << endl;
// subtract 50 years (hoping it is valid and ignoring leap years)
tp -= chrono::duration<int,ratio<3600*24*365>>(50);
cout << "-50 years: " << asString(tp) << endl;
}