How to convert std::chrono::time_point to calendar datetime string with fractional seconds?

Question

How to convert std::chrono::time_point to calendar datetime string with fractional seconds?

For example:

\"10-10-2012 12:38:40.123456\"         


        

Answer 1

In general, you can't do this in any straightforward fashion. time_point is essentially just a duration from a clock-specific epoch.

If you have a std::chrono::system_clock::time_point, then you can use std::chrono::system_clock::to_time_t to convert the time_point to a time_t, and then use the normal C functions such as ctime or strftime to format it.

---

Example code:

std::chrono::system_clock::time_point tp = std::chrono::system_clock::now();
std::time_t time = std::chrono::system_clock::to_time_t(tp);
std::tm timetm = *std::localtime(&time);
std::cout << "output : " << std::put_time(&timetm, "%c %Z") << "+"
          << std::chrono::duration_cast(tp.time_since_epoch()).count() % 1000 << std::endl;