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


Question

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

2015/06/16
1
469
6/16/2015 8:35:43 PM

Accepted Answer

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
2018/12/19
624
12/19/2018 12:42:02 PM


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

2014/03/12

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);
2015/12/01

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;
}
2011/07/13

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

Update for C++20

This library is now largely adopted for C++20. The namespace date is gone and everything is in namespace std::chrono now. And use zoned_time in place of make_time. Drop the headers "date.h" and "tz.h" and just use <chrono>.

As I write this, partial implementations are just beginning to emerge on some platforms.

2020/05/27

(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();
2012/10/20

Source: https://stackoverflow.com/questions/997946
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