C ++日期和时间 [英] C++ date and time

问题描述

我正在C ++开发一个预约应用程序，并希望使用一些日期和时间功能。

在谈论日期和时间时，使用字符串更容易，或者我应该写一个日期/时间类吗？

我想要编写一个约会时间和日期的约会类。一旦我编写了类文件，我想将它集成到C ++构建器中的表单应用程序。

我看到有一个TMonthCalendar控件。我想在使用表单应用程序时使用此控件。这样，这个控制使用什么格式的日期？我想在制作课程时使用与控件相同的类型，以便我可以轻松地将其集成在一起。

更新

我发现它使用TDateTime类型。我的问题是：我需要使用什么语句来在控制台应用程序中使用它？

解决方案

C ++ 11包括日期/时间表示的便利数据类型和功能，以及它们转换为字符串。

可以这样做（很简单，我想）：

  #include< iostream> 
 #include< iomanip> 
 #include< ctime> 
 
 int main（）
 {
 std :: time_t t = std :: time（NULL）; 
 std :: tm tm = * std :: localtime（& t）; 
 std :: cout<<< 现在的时间是<< std :: put_time（& tm，％c％Z）<< '\\\
'; 
} 
  

特别是，有数据类型 std :: time_t 和 std :: tm ，一个非常好的IO操纵器 std :: put_time 为漂亮的打印。其使用的格式字符串在 cppreference 中有详细记录。

这也应该与语言环境一起工作，例如对于日语时间/日期格式：

  std :: cout.imbue（std :: locale（ja_JP.utf8） ）; 
 std :: cout<<< ja_JP：<< std :: put_time（& tm，％c％Z）<< '\\\
'; 
  

C ++包含的 chrono +11标准库还允许您方便地执行简单的时间/日期算术：

  std :: chrono :: time_point< std： ：chrono :: system_clock>现在; 
 now = std :: chrono :: system_clock :: now（）; 
 / *今天前一天：* / 
 std :: time_t now_c = std :: chrono :: system_clock :: to_time_t（
 now  -  std :: chrono :: hours（24） ）; 
  

不幸的是，并不是所有的编译器都可用。特别是，在GCC 4.7.1中似乎没有可以使用 std :: put_time 函数。为了获得我最初提供的代码，我不得不使用稍微优雅的 std :: strftime 函数：

  #include< iostream> 
 #include< iomanip> 
 #include< ctime> 
 
 int main（）
 {
 std :: time_t t = std :: time（NULL）; 
 std :: tm tm = * std :: localtime（& t）; 
 
 constexpr int bufsize = 100; 
 char buf [bufsize]; 
 if（std :: strftime（buf，bufsize，％c％Z，& tm）！= 0）
 std :: cout<< 现在的时间是<< buf< std :: endl; 
} 
  

I am developing an Appointment application in C++ and want to use some Date and Time features.

Is it easier to just use strings when talking about Date and Time, or should I write or get a Date/Time class?

I am wanting to code an appointment class that holds both the time and date of an appointment. Once I have coded the class file, I am wanting to integrate it into a forms application in C++ builder.

I see that there is a TMonthCalendar control. I would like to use this control when making the forms application. As such, what format for the date does this control use? I would like to use the same type as the control when making the class so that I can easily integrate it together.

UPDATE

I have found that it uses the TDateTime type. My question is this: What include statement do I need to use to use this in a console application?

解决方案

C++11 includes convenience data types and functions for date/time representations, as well as their conversion to strings.

With that, you can do things like this (pretty self-explanatory, I think):

#include <iostream>
#include <iomanip>
#include <ctime>

int main()
{
    std::time_t t =  std::time(NULL);
    std::tm tm    = *std::localtime(&t);
    std::cout << "Time right now is " << std::put_time(&tm, "%c %Z") << '\n';
}

In particular, there are data types std::time_t and std::tm, and a very nice IO manipulator std::put_time for pretty printing. The format strings used by it are well-documented at cppreference.

This is also supposed to work together well with locales, e.g. for a Japanese time/date format:

std::cout.imbue(std::locale("ja_JP.utf8"));
std::cout << "ja_JP: " << std::put_time(&tm, "%c %Z") << '\n';

The chrono library included in the C++11 standard library also allows you to do simple time/date arithmetic conveniently:

std::chrono::time_point<std::chrono::system_clock> now;
now = std::chrono::system_clock::now();
/* The day before today: */
std::time_t now_c = std::chrono::system_clock::to_time_t(
         now - std::chrono::hours(24));

Unfortunately, not all of this is available in all compilers yet. In particular, the std::put_time function does not seem to be available in GCC 4.7.1 yet. To get the code I gave initially to work, I had to use the slightly less elegant std::strftime function:

#include <iostream>
#include <iomanip>
#include <ctime>

int main()
{
    std::time_t t =  std::time(NULL);
    std::tm tm    = *std::localtime(&t);

    constexpr int bufsize = 100;
    char buf[bufsize];
    if (std::strftime(buf,bufsize,"%c %Z",&tm) != 0)
      std::cout << "Time right now is " << buf << std::endl;
}

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