How do I construct an ISO 8601 datetime in C++?

Question

I\'m working with the Azure REST API and they are using this to create the request body for table storage:

DateTime.UtcNow.ToString(\"o\")

Answer 1

Tested in Visual C++, GNU C++, Emscripten

#include 
#include 
#include  
#include   

#if defined (_WIN32) 
#define WINDOWSLIB 1
#elif defined (__APPLE__)//iOS, Mac OS
#define MACOSLIB 1
#elif defined (__LINUX__) || defined(__gnu_linux__) || defined(__linux__) || defined(__linux) || defined(linux)//_Ubuntu - Fedora - Centos - RedHat
#define LINUXLIB 1
#elif defined (__EMSCRIPTEN__)
#define EMSCRIPTENLIB 1
#endif

#define WriteLine(data)std::cout<< data <(now.time_since_epoch()).count() % static_cast(1000)));
    if (toUTC)
    {
#ifdef WINDOWSLIB
        gmtime_s(&tm, &timet);
#elif LINUXLIB
        gmtime_r(&timet, &tm);
#elif EMSCRIPTENLIB
        gmtime_r(&timet, &tm);
#endif
        format = format.append(u8"Z");
    }
    else
    {
#ifdef WINDOWSLIB
        localtime_s(&tm, &timet);
#elif LINUXLIB
        localtime_r(&timet, &tm);
#elif EMSCRIPTENLIB
        localtime_r(&timet, &tm);
#endif
        format.append(u8"%z");
    }
    String result = String(255, 0);
    const size_t length = std::strftime(&result[0], result.size(), format.c_str(), &tm);
    result.resize(length);
    setlocale(LC_ALL, localeStr.c_str());
    return result;
}

#define ConsoleWriteLn(data) std::cout<< data <

---

Results

UTC : 2020-04-12T17:00:18.632Z
LOCAL: 2020-04-12T12:00:18.633-0500

You can deserialize normally with Json.NET