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++?

Answer 1

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;
} 

Answer 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";
}

Answer 3

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;
}

Answer 4

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.

Answer 5

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();
}

Answer 6

std::ctime

Why was ctime only mentioned in the comments so far?

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

Output

Tue Dec 27 17:21:29 2011