How to get current time and date in C++?

问题:

Is there a cross-platform way to get the current date and time in C++?

回答1:

In C++ 11 you can use std::chrono::system_clock::now()

Example (copied from en.cppreference.com):

#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:

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

回答2:

C++ shares its date/time functions with C. The tm structure is probably the easiest for a C++ programmer to work with - the following prints today\'s date:

#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3:

You can try the following cross-platform code to get current date/time:

#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:

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

Please visit here for more information about date/time format

回答4:

std C libraries provide time(). This is seconds from the epoch and can be converted to date and H:M:S using standard C functions. Boost also has a time/date library that you can check.

time_t  timev;
time(&timev);

回答5:

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.

// 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6:

New answer for an old question:

The question does not specify in what timezone. There are two reasonable possibilities:

1. In UTC.
2. In the computer\'s local timezone.

For 1, you can use this date library and the following program:

#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:

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.

If you prefer 2 (the local time), there is a timezone library that builds on top of the date library. Both of these libraries are open source and cross platform, assuming the compiler supports C++11 or 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:

2015-08-18 18:08:18.944211 EDT

The result type from make_zoned is a date::zoned_time which is a pairing of a date::time_zone and a std::chrono::system_clock::time_point. This pair represents a local time, but can also represent UTC, depending on how you query it.

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.

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 local to:

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

And the output changes to:

2015-08-19 08:08:18.944211 AEST

回答7:

(For fellow googlers)

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8:

#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9:

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).

std::put_time() (C++11) and strftime() (C) offer a lot of formatters to output those times.

#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:

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:

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).

---

Locale settings alter the output:

#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):

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.

Heed that asctime()/ctime() which were mentioned in other answers are marked as deprecated now and strftime() should be preferred.

回答10:

Yes and you can do so with formatting rules specified by the currently-imbued locale:

#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

回答11:

you could use C++ 11 time class:

    #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;
     }

out put:

2017-08-25 12:30:08

回答12:

There\'s always the __TIMESTAMP__ preprocessor macro.

#include <iostream>

using namespace std

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

int main() {
    printBuildDateTime();
}

example: Sun Apr 13 11:28:08 2014

回答13:

You can also directly use 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;
} 

回答14:

I found this link pretty useful for my implementation: C++ Date and Time

Here\'s the code I use in my implementation, to get a clear \"YYYYMMDD HHMMSS\" output format. The param in is for switching between UTC and local time. You can easily modify my code to suite your need.

#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();
}

Output (UTC, EST):

20161123 000454
20161122 190454

回答15:

This compiled for me on Linux (RHEL) and Windows (x64) targeting g++ and 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;
}

回答16:

The ffead-cpp provides multiple utility classes for various tasks, one such class is the Date class which provides a lot of features right from Date operations to date arithmetic, there\'s also a Timer class provided for timing operations. You can have a look at the same.

回答17:

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

This built-in seems to offer a reasonable set of options.

回答18:

This works with G++ I\'m not sure if this helps you. Program output:

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.

Code :

#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;  
}

回答19:

localtime_s() version:

#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;
} 

回答20:

#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)

}

回答21:

You could use boost:

#include <boost/date_time/gregorian/gregorian.hpp>
#include <iostream>
using namespace boost::gregorian;

int main()
{
    date d = day_clock::universal_day();
    std::cout << d.day() << \" \" << d.month() << \" \" << d.year();
}

回答22:

You can use the following code to get the current system date and time in C++ :

#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;
}

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