time_t  timev;
time(&timev);

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——下面打印今天的日期:

#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";
}

c++标准库没有提供合适的日期类型。c++继承了C语言中用于日期和时间操作的结构和函数，以及一些考虑本地化的日期/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;
}

#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;
}

你可以尝试下面的跨平台代码来获取当前的日期/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
}

输出:

currentDateTime()=2012-05-06.21:47:59

有关日期/时间格式的更多信息，请访问在这里

ffead-cpp为各种任务提供了多个实用程序类，其中一个这样的类是日期类，它提供了从日期操作到日期算术的许多特性，还有一个计时器类提供了定时操作。你也可以看看。

(给谷歌人)

还有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();

你也可以直接使用ctime():

#include <stdio.h>
#include <time.h>


int main ()
{
time_t rawtime;
struct tm * timeinfo;


time ( &rawtime );
printf ( "Current local time and date: %s", ctime (&rawtime) );


return 0;
}

是的，你可以这样做的格式规则指定的当前填充区域:

#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");
}

输出:# EYZ0

总有__TIMESTAMP__预处理器宏。

#include <iostream>


using namespace std


void printBuildDateTime () {
cout << __TIMESTAMP__ << endl;
}


int main() {
printBuildDateTime();
}

例:2014年4月13日太阳11:28:08

#include <Windows.h>


void main()
{
//Following is a structure to store date / time


SYSTEMTIME SystemTime, LocalTime;


//To get the local time


int loctime = GetLocalTime(&LocalTime);


//To get the system time


int systime = GetSystemTime(&SystemTime)


}

http://www.cplusplus.com/reference/ctime/strftime/

这个内置功能似乎提供了一组合理的选项。

从c++ 11开始，你可以使用std::chrono::system_clock::now()

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"
<< std::endl;
}

这应该打印如下内容:

finished computation at Mon Oct  2 00:59:08 2017
elapsed time: 1.88232s

The current time is 11:43:41 am
The current date is 6-18-2015 June Wednesday
Day of month is 17 and the Month of year is 6,
also the day of year is 167 & our Weekday is 3.
The current year is 2015.

代码:

#include <ctime>
#include <iostream>
#include <string>
#include <stdio.h>
#include <time.h>


using namespace std;


const std::string currentTime() {
time_t now = time(0);
struct tm tstruct;
char buf[80];
tstruct = *localtime(&now);
strftime(buf, sizeof(buf), "%H:%M:%S %P", &tstruct);
return buf;
}


const std::string currentDate() {
time_t now = time(0);
struct tm tstruct;
char buf[80];
tstruct = *localtime(&now);
strftime(buf, sizeof(buf), "%B %A ", &tstruct);
return buf;
}


int main() {
cout << "\033[2J\033[1;1H";
std:cout << "The current time is " << currentTime() << std::endl;
time_t t = time(0);   // get time now
struct tm * now = localtime( & t );
cout << "The current date is " << now->tm_mon + 1 << '-'
<< (now->tm_mday  + 1) << '-'
<<  (now->tm_year + 1900)
<< " " << currentDate() << endl;


cout << "Day of month is " << (now->tm_mday)
<< " and the Month of year is " << (now->tm_mon)+1 << "," << endl;
cout << "also the day of year is " << (now->tm_yday)
<< " & our Weekday is " << (now->tm_wday) << "." << endl;
cout << "The current year is " << (now->tm_year)+1900 << "."
<< endl;
return 0;
}

老问题的新答案:

这个问题没有指定在哪个时区。有两种合理的可能性:

1. 在UTC。
2. 在计算机的本地时区。

对于1，你可以使用这个日期库和下面的程序:

#include "date.h"
#include <iostream>


int
main()
{
using namespace date;
using namespace std::chrono;
std::cout << system_clock::now() << '\n';
}

这对我来说只是输出:

2015-08-18 22:08:18.944211

日期库实际上只是为std::chrono::system_clock::time_point添加了一个流操作符。它还添加了许多其他不错的功能，但在这个简单的程序中没有使用这些功能。

如果您更喜欢2(本地时间)，则在日期图书馆之上构建时区图书馆。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';
}

这对我来说只是输出:

2015-08-18 18:08:18.944211 EDT

make_zoned的结果类型是date::zoned_time，它是date::time_zone和std::chrono::system_clock::time_point的配对。这个时间对表示本地时间，但也可以表示UTC，这取决于您如何查询它。

通过上面的输出，您可以看到我的计算机目前处于UTC偏移量为-4h的时区，以及EDT的缩写。

如果需要使用其他时区，也可以实现这一点。例如，要查找澳大利亚悉尼的当前时间，只需将变量local的结构更改为:

auto local = make_zoned("Australia/Sydney", system_clock::now());

输出变为:

2015-08-19 08:08:18.944211 AEST

适用于c++ 20

这个库现在在c++ 20中被广泛采用。命名空间date消失了，现在所有内容都在命名空间std::chrono中。用zoned_time代替make_time。删除标题"date.h"和"tz.h"，只使用<chrono>。

#include <chrono>
#include <iostream>


int
main()
{
using namespace std::chrono;
auto local = zoned_time{current_zone(), system_clock::now()};
std::cout << local << '\n';  // 2021-05-03 15:02:44.130182 EDT
}

在我写这篇文章的时候，部分实现刚刚开始出现在一些平台上。

你可以使用boost和chrono库:

#include <iostream>
#include <chrono>
#include <boost/date_time/posix_time/posix_time.hpp>


using boost::posix_time::to_iso_extended_string;
using boost::posix_time::from_time_t;
using std::chrono::system_clock;


int main()
{
auto now = system_clock::now();
std::cout << to_iso_extended_string(from_time_t(system_clock::to_time_t(now)));
}

这为我在Linux (RHEL)和Windows (x64)上编译，目标是g++和OpenMP:

#include <ctime>
#include <iostream>
#include <string>
#include <locale>


////////////////////////////////////////////////////////////////////////////////
//
//  Reports a time-stamped update to the console; format is:
//       Name: Update: Year-Month-Day_of_Month Hour:Minute:Second
//
////////////////////////////////////////////////////////////////////////////////
//
//  [string] strName  :  name of the update object
//  [string] strUpdate:  update descripton
//
////////////////////////////////////////////////////////////////////////////////


void ReportTimeStamp(string strName, string strUpdate)
{
try
{
#ifdef _WIN64
//  Current time
const time_t tStart = time(0);
//  Current time structure
struct tm tmStart;


localtime_s(&tmStart, &tStart);


//  Report
cout << strName << ": " << strUpdate << ": " << (1900 + tmStart.tm_year) << "-" << tmStart.tm_mon << "-" << tmStart.tm_mday << " " << tmStart.tm_hour << ":" << tmStart.tm_min << ":" << tmStart.tm_sec << "\n\n";
#else
//  Current time
const time_t tStart = time(0);
//  Current time structure
struct tm* tmStart;


tmStart = localtime(&tStart);


//  Report
cout << strName << ": " << strUpdate << ": " << (1900 + tmStart->tm_year) << "-" << tmStart->tm_mon << "-" << tmStart->tm_mday << " " << tmStart->tm_hour << ":" << tmStart->tm_min << ":" << tmStart->tm_sec << "\n\n";
#endif


}
catch (exception ex)
{
cout << "ERROR [ReportTimeStamp] Exception Code:  " << ex.what() << "\n";
}


return;
}

下面是我在实现中使用的代码，以获得清晰的“YYYYMMDD HHMMSS”输出格式。参数in用于在UTC和本地时间之间切换。您可以轻松地修改我的代码以满足您的需要。

#include <iostream>
#include <ctime>


using namespace std;


/**
* This function gets the current date time
* @param useLocalTime true if want to use local time, default to false (UTC)
* @return current datetime in the format of "YYYYMMDD HHMMSS"
*/


string getCurrentDateTime(bool useLocalTime) {
stringstream currentDateTime;
// current date/time based on current system
time_t ttNow = time(0);
tm * ptmNow;


if (useLocalTime)
ptmNow = localtime(&ttNow);
else
ptmNow = gmtime(&ttNow);


currentDateTime << 1900 + ptmNow->tm_year;


//month
if (ptmNow->tm_mon < 9)
//Fill in the leading 0 if less than 10
currentDateTime << "0" << 1 + ptmNow->tm_mon;
else
currentDateTime << (1 + ptmNow->tm_mon);


//day
if (ptmNow->tm_mday < 10)
currentDateTime << "0" << ptmNow->tm_mday << " ";
else
currentDateTime <<  ptmNow->tm_mday << " ";


//hour
if (ptmNow->tm_hour < 10)
currentDateTime << "0" << ptmNow->tm_hour;
else
currentDateTime << ptmNow->tm_hour;


//min
if (ptmNow->tm_min < 10)
currentDateTime << "0" << ptmNow->tm_min;
else
currentDateTime << ptmNow->tm_min;


//sec
if (ptmNow->tm_sec < 10)
currentDateTime << "0" << ptmNow->tm_sec;
else
currentDateTime << ptmNow->tm_sec;




return currentDateTime.str();
}

输出(UTC, EST):

20161123 000454
20161122 190454

auto time = std::time(nullptr);
std::cout << std::put_time(std::localtime(&time), "%F %T%z"); // ISO 8601 format.

使用std::time()或std::chrono::system_clock::now()(或另一个时钟类型)获取当前时间。

std::put_time() (c++ 11)和strftime() (C)提供了许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");
}

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

strftime()的格式化器类似:

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
}

通常，大写格式器表示“完整版本”，小写格式器表示缩写(例如Y: 2017, Y: 17)。

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");
}

可能输出(Coliru， 编译器的探险家):

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

我使用std::gmtime()转换为UTC。std::localtime()用于转换为本地时间。

注意，在其他答案中提到的asctime()/ctime()现在被标记为不赞成，strftime()应该是首选。

localtime_s()版本:

#include <stdio.h>
#include <time.h>


int main ()
{
time_t current_time;
struct tm  local_time;


time ( &current_time );
localtime_s(&local_time, &current_time);


int Year   = local_time.tm_year + 1900;
int Month  = local_time.tm_mon + 1;
int Day    = local_time.tm_mday;


int Hour   = local_time.tm_hour;
int Min    = local_time.tm_min;
int Sec    = local_time.tm_sec;


return 0;
}

你可以使用c++ 11时间类:

    #include <iostream>
#include <iomanip>
using namespace std;


int main() {


time_t now = chrono::system_clock::to_time_t(chrono::system_clock::now());
cout << put_time(localtime(&now), "%F %T") <<  endl;
return 0;
}

把:

2017-08-25 12:30:08

你可以使用下面的代码来获得c++中的当前系统日期和时间:

    #include <iostream>
#include <time.h> //It may be #include <ctime> or any other header file depending upon
// compiler or IDE you're using
using namespace std;


int main() {
// current date/time based on current system
time_t now = time(0);


// convert now to string form
string dt = ctime(&now);


cout << "The local date and time is: " << dt << endl;
return 0;
}

# EYZ0 # EYZ1

#include <iostream>
#include <chrono>
#include <string>
#pragma warning(disable: 4996)
// Ver: C++ 17
// IDE: Visual Studio
int main() {
using namespace std;
using namespace chrono;
time_point tp = system_clock::now();
time_t tt = system_clock::to_time_t(tp);
cout << "Current time: " << ctime(&tt) << endl;
return 0;
}

std:: ctime

为什么到目前为止，ctime只在评论中被提及?

#include <ctime>
#include <iostream>
 

int main()
{
std::time_t result = std::time(nullptr);
std::cout << std::ctime(&result);
}

输出

# EYZ0

下面是不弃用的现代c++解决方案，用于获得一个std::string的时间戳，用于例如文件名:

std::string get_file_timestamp()
{
const auto now = std::chrono::system_clock::now();
const auto in_time_t = std::chrono::system_clock::to_time_t(now);


std::stringstream output_stream;


struct tm time_info;
const auto errno_value = localtime_s(&time_info, &in_time_t);
if(errno_value != 0)
{
throw std::runtime_error("localtime_s() failed: " + std::to_string(errno_value));
}


output_stream << std::put_time(&time_info, "%Y-%m-%d.%H_%M_%S");
return output_stream.str();
}

#include<bits/stdc++.h>
#include<unistd.h>
using namespace std;
int main()
{   //initialize variables
time_t now;
//blah..blah
/*each time I want the updated stamp*/
now=time(0);cout<<ctime(&now)<<"blah_blah";
}