如何在 C++ 中获取当前时间和日期？
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原文地址: http://stackoverflow.com/questions/997946/
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How to get current time and date in C++?
提问by Max Frai
Is there a cross-platform way to get the current date and time in C++?
是否有跨平台的方式来获取 C++ 中的当前日期和时间？
回答by Frederick The Fool
In C++ 11 you can use std::chrono::system_clock::now()
在 C++ 11 中，您可以使用 std::chrono::system_clock::now()
Example (copied from en.cppreference.com):
示例（从en.cppreference.com复制）：
#include <iostream>
#include <chrono>
#include <ctime>
int main()
{
auto start = std::chrono::system_clock::now();
// Some computation here
auto end = std::chrono::system_clock::now();
std::chrono::duration<double> elapsed_seconds = end-start;
std::time_t end_time = std::chrono::system_clock::to_time_t(end);
std::cout << "finished computation at " << std::ctime(&end_time)
<< "elapsed time: " << elapsed_seconds.count() << "s\n";
}
This should print something like this:
这应该打印如下内容：
finished computation at Mon Oct 2 00:59:08 2017
elapsed time: 1.88232s
回答by Frederick The Fool
C++ shares its date/time functions with C. The tm structureis probably the easiest for a C++ programmer to work with - the following prints today's date:
C++ 与 C 共享它的日期/时间函数。tm 结构可能是 C++ 程序员最容易使用的 - 以下打印今天的日期：
#include <ctime>
#include <iostream>
int main() {
std::time_t t = std::time(0); // get time now
std::tm* now = std::localtime(&t);
std::cout << (now->tm_year + 1900) << '-'
<< (now->tm_mon + 1) << '-'
<< now->tm_mday
<< "\n";
}
回答by TrungTN
You can try the following cross-platform code to get current date/time:
您可以尝试以下跨平台代码来获取当前日期/时间：
#include <iostream>
#include <string>
#include <stdio.h>
#include <time.h>
// Get current date/time, format is YYYY-MM-DD.HH:mm:ss
const std::string currentDateTime() {
time_t now = time(0);
struct tm tstruct;
char buf[80];
tstruct = *localtime(&now);
// Visit http://en.cppreference.com/w/cpp/chrono/c/strftime
// for more information about date/time format
strftime(buf, sizeof(buf), "%Y-%m-%d.%X", &tstruct);
return buf;
}
int main() {
std::cout << "currentDateTime()=" << currentDateTime() << std::endl;
getchar(); // wait for keyboard input
}
Output:
输出：
currentDateTime()=2012-05-06.21:47:59
Please visit herefor more information about date/time format
请访问此处了解有关日期/时间格式的更多信息
回答by Martin York
std C libraries provide time().
This is seconds from the epoch and can be converted to date and H:M:Susing standard C functions. Boostalso has a time/date librarythat you can check.
std C 库提供time(). 这是从纪元开始的几秒钟，可以转换为日期并H:M:S使用标准 C 函数。Boost还有一个时间/日期库，您可以查看。
time_t timev;
time(&timev);
回答by Vaibhav Patle
the C++ standard library does not provide a proper date type. C++ inherits the structs and functions for date and time manipulation from C, along with a couple of date/time input and output functions that take into account localization.
C++ 标准库没有提供正确的日期类型。C++ 从 C 继承了用于日期和时间操作的结构和函数，以及一些考虑到本地化的日期/时间输入和输出函数。
// Current date/time based on current system
time_t now = time(0);
// Convert now to tm struct for local timezone
tm* localtm = localtime(&now);
cout << "The local date and time is: " << asctime(localtm) << endl;
// Convert now to tm struct for UTC
tm* gmtm = gmtime(&now);
if (gmtm != NULL) {
cout << "The UTC date and time is: " << asctime(gmtm) << endl;
}
else {
cerr << "Failed to get the UTC date and time" << endl;
return EXIT_FAILURE;
}
回答by Howard Hinnant
New answer for an old question:
旧问题的新答案：
The question does not specify in what timezone. There are two reasonable possibilities:
问题没有指定在哪个时区。有两种合理的可能性：
- In UTC.
- In the computer's local timezone.
- 在 UTC。
- 在计算机的本地时区。
For 1, you can use this date libraryand the following program:
对于 1，您可以使用此日期库和以下程序：
#include "date.h"
#include <iostream>
int
main()
{
using namespace date;
using namespace std::chrono;
std::cout << system_clock::now() << '\n';
}
Which just output for me:
这只是为我输出：
2015-08-18 22:08:18.944211
The date library essentially just adds a streaming operator for std::chrono::system_clock::time_point. It also adds a lot of other nice functionality, but that is not used in this simple program.
日期库本质上只是为std::chrono::system_clock::time_point. 它还添加了许多其他不错的功能，但是在这个简单的程序中没有使用这些功能。
If you prefer 2 (the local time), there is a timezone librarythat builds on top of the date library. Both of these libraries are open sourceand cross platform, assuming the compiler supports C++11 or C++14.
如果您更喜欢 2（本地时间），则有一个建立在日期库之上的时区库。这两个库都是开源和跨平台的，假设编译器支持 C++11 或 C++14。
#include "tz.h"
#include <iostream>
int
main()
{
using namespace date;
using namespace std::chrono;
auto local = make_zoned(current_zone(), system_clock::now());
std::cout << local << '\n';
}
Which for me just output:
这对我来说只是输出：
2015-08-18 18:08:18.944211 EDT
The result type from make_zonedis a date::zoned_timewhich is a pairing of a date::time_zoneand a std::chrono::system_clock::time_point. This pair represents a local time, but can also represent UTC, depending on how you query it.
结果类型 frommake_zoned是 a date::zoned_time，它是 adate::time_zone和 a的配对std::chrono::system_clock::time_point。这对表示本地时间，但也可以表示 UTC，具体取决于您查询它的方式。
With the above output, you can see that my computer is currently in a timezone with a UTC offset of -4h, and an abbreviation of EDT.
通过上面的输出，您可以看到我的计算机当前处于 UTC 偏移量为 -4h 且缩写为 EDT 的时区。
If some other timezone is desired, that can also be accomplished. For example to find the current time in Sydney , Australia just change the construction of the variable localto:
如果需要其他时区，也可以实现。例如，要查找澳大利亚悉尼的当前时间，只需将变量的构造更改local为：
auto local = make_zoned("Australia/Sydney", system_clock::now());
And the output changes to:
并且输出更改为：
2015-08-19 08:08:18.944211 AEST
Update for C++20
C++20 更新
This library is now largely adopted for C++20. The namespace dateis gone and everything is in namespace std::chrononow. And use zoned_timein place of make_time. Drop the headers "date.h"and "tz.h"and just use <chrono>.
该库现在主要用于 C++20。命名空间date消失了，std::chrono现在一切都在命名空间中。并zoned_time代替make_time. 删除标题"date.h"，"tz.h"然后使用<chrono>.
As I write this, partial implementations are just beginning to emerge on some platforms.
在我撰写本文时，部分实现才刚刚开始在某些平台上出现。
回答by Offirmo
(For fellow googlers)
（对于谷歌同事）
There is also Boost::date_time:
#include <boost/date_time/posix_time/posix_time.hpp>
boost::posix_time::ptime date_time = boost::posix_time::microsec_clock::universal_time();
回答by Roi Danton
auto time = std::time(nullptr);
std::cout << std::put_time(std::localtime(&time), "%F %T%z"); // ISO 8601 format.
Get the current time either using std::time()or std::chrono::system_clock::now()(or another clock type).
使用std::time()或std::chrono::system_clock::now()（或其他时钟类型）获取当前时间。
std::put_time()(C++11) and strftime()(C) offer a lot of formatters to output those times.
std::put_time()(C++11) 和strftime()(C) 提供了很多格式化程序来输出这些时间。
#include <iomanip>
#include <iostream>
int main() {
auto time = std::time(nullptr);
std::cout
// ISO 8601: %Y-%m-%d %H:%M:%S, e.g. 2017-07-31 00:42:00+0200.
<< std::put_time(std::gmtime(&time), "%F %T%z") << '\n'
// %m/%d/%y, e.g. 07/31/17
<< std::put_time(std::gmtime(&time), "%D");
}
The sequence of the formatters matters:
格式化程序的顺序很重要：
std::cout << std::put_time(std::gmtime(&time), "%c %A %Z") << std::endl;
// Mon Jul 31 00:00:42 2017 Monday GMT
std::cout << std::put_time(std::gmtime(&time), "%Z %c %A") << std::endl;
// GMT Mon Jul 31 00:00:42 2017 Monday
The formatters of strftime()are similar:
的格式化程序strftime()类似：
char output[100];
if (std::strftime(output, sizeof(output), "%F", std::gmtime(&time))) {
std::cout << output << '\n'; // %Y-%m-%d, e.g. 2017-07-31
}
Often, the capital formatter means "full version" and lowercase means abbreviation (e.g. Y: 2017, y: 17).
通常，大写格式表示“完整版”，小写表示缩写（例如 Y: 2017, y: 17）。
Locale settings alter the output:
区域设置改变输出：
#include <iomanip>
#include <iostream>
int main() {
auto time = std::time(nullptr);
std::cout << "undef: " << std::put_time(std::gmtime(&time), "%c") << '\n';
std::cout.imbue(std::locale("en_US.utf8"));
std::cout << "en_US: " << std::put_time(std::gmtime(&time), "%c") << '\n';
std::cout.imbue(std::locale("en_GB.utf8"));
std::cout << "en_GB: " << std::put_time(std::gmtime(&time), "%c") << '\n';
std::cout.imbue(std::locale("de_DE.utf8"));
std::cout << "de_DE: " << std::put_time(std::gmtime(&time), "%c") << '\n';
std::cout.imbue(std::locale("ja_JP.utf8"));
std::cout << "ja_JP: " << std::put_time(std::gmtime(&time), "%c") << '\n';
std::cout.imbue(std::locale("ru_RU.utf8"));
std::cout << "ru_RU: " << std::put_time(std::gmtime(&time), "%c");
}
Possible output (Coliru, Compiler Explorer):
可能的输出（Coliru，Compiler Explorer）：
undef: Tue Aug 1 08:29:30 2017
en_US: Tue 01 Aug 2017 08:29:30 AM GMT
en_GB: Tue 01 Aug 2017 08:29:30 GMT
de_DE: Di 01 Aug 2017 08:29:30 GMT
ja_JP: 2017年08月01日 08時29分30秒
ru_RU: Вт 01 авг 2017 08:29:30
I've used std::gmtime()for conversion to UTC. std::localtime()is provided to convert to local time.
我已经用于std::gmtime()转换为 UTC。std::localtime()提供转换为本地时间。
Heed that asctime()/ctime()which were mentioned in other answers are marked as deprecated now and strftime()should be preferred.
回答by etcheve
#include <stdio.h>
#include <time.h>
int main ()
{
time_t rawtime;
struct tm * timeinfo;
time ( &rawtime );
timeinfo = localtime ( &rawtime );
printf ( "Current local time and date: %s", asctime (timeinfo) );
return 0;
}
回答by 0x499602D2
Yes and you can do so with formatting rules specified by the currently-imbued locale:
是的，您可以使用当前流行的语言环境指定的格式规则来执行此操作：
#include <iostream>
#include <iterator>
#include <string>
class timefmt
{
public:
timefmt(std::string fmt)
: format(fmt) { }
friend std::ostream& operator <<(std::ostream &, timefmt const &);
private:
std::string format;
};
std::ostream& operator <<(std::ostream& os, timefmt const& mt)
{
std::ostream::sentry s(os);
if (s)
{
std::time_t t = std::time(0);
std::tm const* tm = std::localtime(&t);
std::ostreambuf_iterator<char> out(os);
std::use_facet<std::time_put<char>>(os.getloc())
.put(out, os, os.fill(),
tm, &mt.format[0], &mt.format[0] + mt.format.size());
}
os.width(0);
return os;
}
int main()
{
std::cout << timefmt("%c");
}
Output:
Fri Sep 6 20:33:31 2013
输出：
Fri Sep 6 20:33:31 2013
