I'm running into a error trying to compile the program with conversion from double to int. What I want is to be able to display out the difference not just in seconds but in hours/minutes/seconds but I can't think of how to make the difftime work. If there is a better option like using chrono, I would appreciate the help.
#include <chrono>
#include <ctime>
#include <iomanip>
#include <iostream>
int main() {
std::tm now{},;
std::chrono::system_clock::time_point cc;
std::cout << "enter\nyear month day\n";
std::cin >> now.tm_year >> now.tm_mon >> now.tm_mday;
now.tm_year -= 1900;
now.tm_mon -= 1;
std::time_t n = std::mktime(&now);
cc = std::chrono::system_clock::from_time_t(n);
n = std::chrono::system_clock::to_time_t(cc);
std::cout << std::put_time(std::localtime(&n), "%FT%T") << "\n";
std::time_t system_time = time(nullptr);
std::cout << asctime(localtime(&system_time));
double fc = difftime(system_time, mktime(&now));
std::cout << "time diff "<< fc << endl;
}
You should checkout the date lib from howard hinnant.
https://github.com/HowardHinnant/date
The tz lib in it Can do your local time diff calculation in without converting it to utc. (normally you should always convert to utc before calculation, because of the daylight saving time) It also contains format functions to stream it in hour min sec format.
The better way of doing it is using a steady_clock instead of system_clock.
I don't know what your task is but you may use another class such as Stopwatch to generate elapsed time.
#include <chrono>
#include <ctime>
class StopWatch {
private:
chrono::time_point<chrono::steady_clock> start;
public:
void reset() { start = chrono::steady_clock::now(); }
StopWatch() { reset(); }
double elapsedSeconds() {
chrono::duration<double> d = chrono::steady_clock::now() - start;
return chrono::duration_cast<chrono::microseconds>(d).count() / 1000000.;
}};
After that, you can simply use Stopwatch:
int main(void){
Stopwatch s;
cout<<s.elapsedSeconds();
}
I am trying to find some utility in the chrono namespace to provide to my application the same feature I had in my C# program. What I need to do is to compute the time difference between to specific dates, but I can't find anything this specific. For example following is my C# code:
var startDate = new DateTime(2000, 1, 1);
int diffDays = (DateTime.Today.Date - startDate.Date).Days;
return diffDays.ToString();
Is there any equivalent function in C++?
// system_clock::from_time_t
#include <iostream>
#include <ctime>
#include <ratio>
#include <chrono>
int main ()
{
using namespace std::chrono;
// create tm with 1/1/2000:
std::tm timeinfo = std::tm();
timeinfo.tm_year = 100; // year: 2000
timeinfo.tm_mon = 0; // month: january
timeinfo.tm_mday = 1; // day: 1st
std::time_t tt = std::mktime (&timeinfo);
system_clock::time_point tp = system_clock::from_time_t (tt);
system_clock::duration d = system_clock::now() - tp;
// convert to number of days:
typedef duration<int,std::ratio<60*60*24>> days_type;
days_type ndays = duration_cast<days_type> (d);
// display result:
std::cout << ndays.count() << " days have passed since 1/1/2000";
std::cout << std::endl;
return 0;
}
Credits: http://www.cplusplus.com/reference/chrono/system_clock/from_time_t/
Here's an easier way to do this using this header-only open source lib:
#include "date.h"
#include <iostream>
int
main()
{
using namespace date;
using namespace std::chrono;
auto startDate = 2000_y/jan/1;
auto diffDays = floor<days>(system_clock::now()) - sys_days{startDate};
std::cout << diffDays.count() << '\n';
}
Currently outputs:
6138
Here is a wandbox link where you can paste the above code and try it out yourself using various versions of gcc and clang.
I am using boost 1.46 which does not include boost::timer, What other way can I time my functions.
I am currently doing this:
time_t now = time(0);
<some stuff>
time_t after = time(0);
cout << after - now << endl;
but it just gives the answer in seconds, so if the function takes < 1s it displays 0.
Thanks
In linux or Windows:
#include <ctime>
#include <iostream>
int
main(int, const char**)
{
std::clock_t start;
start = std::clock();
// your test
std::cout << "Time: " << (std::clock() - start) / (double)(CLOCKS_PER_SEC / 1000) << " ms" << std::endl;
return 0;
}
Good Luck ;)
Using std::chrono:
#include <chrono>
#include <thread>
#include <iostream>
// There are other clocks, but this is usually the one you want.
// It corresponds to CLOCK_MONOTONIC at the syscall level.
using Clock = std::chrono::steady_clock;
using std::chrono::time_point;
using std::chrono::duration_cast;
using std::chrono::milliseconds;
using namespace std::literals::chrono_literals;
using std::this_thread::sleep_for;
int main()
{
time_point<Clock> start = Clock::now();
sleep_for(500ms);
time_point<Clock> end = Clock::now();
milliseconds diff = duration_cast<milliseconds>(end - start);
std::cout << diff.count() << "ms" << std::endl;
}
std::chrono is C++11, std::literals is C++14 (otherwise you need milliseconds(500)).
Turns out there is a version of time in boost 1.46 (just in different location). Thanks to
#jogojapan for pointing it out.
It can be done like this:
#include <boost/timer.hpp>
timer t;
<some stuff>
std::cout << t.elapsed() << std::endl;
Or alternatively using std libs as #Quentin Perez has pointed out (and I will accept as is what was originally asked)
Building on Quentin Perez's solution, you can pass an arbitrary function to time using std::function and a lambda.
#include <ctime>
#include <iostream>
#include <functional>
void timeit(std::function<void()> func) {
std::clock_t start = std::clock();
func();
int ms = (std::clock() - start) / (double) (CLOCKS_PER_SEC / 1000);
std::cout << "Finished in " << ms << "ms" << std::endl;
}
int main() {
timeit([] {
for (int i = 0; i < 10; ++i) {
std::cout << "i = " << i << std::endl;
}
});
return 0;
}
You can use a long to hold the current time value as a start value, and then convert the current time to a double. here is some snippet code to use as an example.
#include <iostream>
#include <stdlib.h>
#include <time.h>
#include <sys/types.h>
#include <sys/timeb.h>
int main()
{
struct _timeb tStruct;
double thisTime;
bool done = false;
long startTime;
struct _timeb
{
int dstflag; // holds a non-zero value if daylight saving time is in effect
long millitm; // time in milliseconds since the last one-second hack
long time; // time in seconds since 00:00:00 1/1/1970
long timezone; // difference in minutes moving west from UTC
};
_ftime(&tStruct); // Get start time
thisTime = tStruct.time + (((double)(tStruct.millitm)) / 1000.0); // Convert to double
startTime = thisTime; // Set the starting time (when the function begins)
while(!done) // Start an eternal loop
{
system("cls"); // Clear the screen
_ftime(&tStruct); // Get the current time
thisTime = tStruct.time + (((double)(tStruct.millitm)) / 1000.0); // Convert to double
// Check for 5 second interval to print status to screen
cout << thisTime-startTime; // Print it.
}
}
How to convert std::chrono::time_point to calendar datetime string with fractional seconds?
For example:
"10-10-2012 12:38:40.123456"
If system_clock, this class have time_t conversion.
#include <iostream>
#include <chrono>
#include <ctime>
using namespace std::chrono;
int main()
{
system_clock::time_point p = system_clock::now();
std::time_t t = system_clock::to_time_t(p);
std::cout << std::ctime(&t) << std::endl; // for example : Tue Sep 27 14:21:13 2011
}
example result:
Thu Oct 11 19:10:24 2012
EDIT:
But, time_t does not contain fractional seconds.
Alternative way is to use time_point::time_since_epoch() function. This function returns duration from epoch.
Follow example is milli second resolution's fractional.
#include <iostream>
#include <chrono>
#include <ctime>
using namespace std::chrono;
int main()
{
high_resolution_clock::time_point p = high_resolution_clock::now();
milliseconds ms = duration_cast<milliseconds>(p.time_since_epoch());
seconds s = duration_cast<seconds>(ms);
std::time_t t = s.count();
std::size_t fractional_seconds = ms.count() % 1000;
std::cout << std::ctime(&t) << std::endl;
std::cout << fractional_seconds << std::endl;
}
example result:
Thu Oct 11 19:10:24 2012
925
Self-explanatory code follows which first creates a std::tm corresponding to 10-10-2012 12:38:40, converts that to a std::chrono::system_clock::time_point, adds 0.123456 seconds, and then prints that out by converting back to a std::tm. How to handle the fractional seconds is in the very last step.
#include <iostream>
#include <chrono>
#include <ctime>
int main()
{
// Create 10-10-2012 12:38:40 UTC as a std::tm
std::tm tm = {0};
tm.tm_sec = 40;
tm.tm_min = 38;
tm.tm_hour = 12;
tm.tm_mday = 10;
tm.tm_mon = 9;
tm.tm_year = 112;
tm.tm_isdst = -1;
// Convert std::tm to std::time_t (popular extension)
std::time_t tt = timegm(&tm);
// Convert std::time_t to std::chrono::system_clock::time_point
std::chrono::system_clock::time_point tp =
std::chrono::system_clock::from_time_t(tt);
// Add 0.123456 seconds
// This will not compile if std::chrono::system_clock::time_point has
// courser resolution than microseconds
tp += std::chrono::microseconds(123456);
// Now output tp
// Convert std::chrono::system_clock::time_point to std::time_t
tt = std::chrono::system_clock::to_time_t(tp);
// Convert std::time_t to std::tm (popular extension)
tm = std::tm{0};
gmtime_r(&tt, &tm);
// Output month
std::cout << tm.tm_mon + 1 << '-';
// Output day
std::cout << tm.tm_mday << '-';
// Output year
std::cout << tm.tm_year+1900 << ' ';
// Output hour
if (tm.tm_hour <= 9)
std::cout << '0';
std::cout << tm.tm_hour << ':';
// Output minute
if (tm.tm_min <= 9)
std::cout << '0';
std::cout << tm.tm_min << ':';
// Output seconds with fraction
// This is the heart of the question/answer.
// First create a double-based second
std::chrono::duration<double> sec = tp -
std::chrono::system_clock::from_time_t(tt) +
std::chrono::seconds(tm.tm_sec);
// Then print out that double using whatever format you prefer.
if (sec.count() < 10)
std::cout << '0';
std::cout << std::fixed << sec.count() << '\n';
}
For me this outputs:
10-10-2012 12:38:40.123456
Your std::chrono::system_clock::time_point may or may not be precise enough to hold microseconds.
Update
An easier way is to just use this date library. The code simplifies down to (using C++14 duration literals):
#include "date.h"
#include <iostream>
#include <type_traits>
int
main()
{
using namespace date;
using namespace std::chrono;
auto t = sys_days{10_d/10/2012} + 12h + 38min + 40s + 123456us;
static_assert(std::is_same<decltype(t),
time_point<system_clock, microseconds>>{}, "");
std::cout << t << '\n';
}
which outputs:
2012-10-10 12:38:40.123456
You can skip the static_assert if you don't need to prove that the type of t is a std::chrono::time_point.
If the output isn't to your liking, for example you would really like dd-mm-yyyy ordering, you could:
#include "date.h"
#include <iomanip>
#include <iostream>
int
main()
{
using namespace date;
using namespace std::chrono;
using namespace std;
auto t = sys_days{10_d/10/2012} + 12h + 38min + 40s + 123456us;
auto dp = floor<days>(t);
auto time = make_time(t-dp);
auto ymd = year_month_day{dp};
cout.fill('0');
cout << ymd.day() << '-' << setw(2) << static_cast<unsigned>(ymd.month())
<< '-' << ymd.year() << ' ' << time << '\n';
}
which gives exactly the requested output:
10-10-2012 12:38:40.123456
Update
Here is how to neatly format the current time UTC with milliseconds precision:
#include "date.h"
#include <iostream>
int
main()
{
using namespace std::chrono;
std::cout << date::format("%F %T\n", time_point_cast<milliseconds>(system_clock::now()));
}
which just output for me:
2016-10-17 16:36:02.975
C++17 will allow you to replace time_point_cast<milliseconds> with floor<milliseconds>. Until then date::floor is available in "date.h".
std::cout << date::format("%F %T\n", date::floor<milliseconds>(system_clock::now()));
Update C++20
In C++20 this is now simply:
#include <chrono>
#include <iostream>
int
main()
{
using namespace std::chrono;
auto t = sys_days{10d/10/2012} + 12h + 38min + 40s + 123456us;
std::cout << t << '\n';
}
Or just:
std::cout << std::chrono::system_clock::now() << '\n';
std::format will be available to customize the output.
In general, you can't do this in any straightforward fashion. time_point is essentially just a duration from a clock-specific epoch.
If you have a std::chrono::system_clock::time_point, then you can use std::chrono::system_clock::to_time_t to convert the time_point to a time_t, and then use the normal C functions such as ctime or strftime to format it.
Example code:
std::chrono::system_clock::time_point tp = std::chrono::system_clock::now();
std::time_t time = std::chrono::system_clock::to_time_t(tp);
std::tm timetm = *std::localtime(&time);
std::cout << "output : " << std::put_time(&timetm, "%c %Z") << "+"
<< std::chrono::duration_cast<std::chrono::milliseconds>(tp.time_since_epoch()).count() % 1000 << std::endl;
This worked for me for a format like YYYY.MM.DD-HH.MM.SS.fff. Attempting to make this code capable of accepting any string format will be like reinventing the wheel (i.e. there are functions for all this in Boost.
std::chrono::system_clock::time_point string_to_time_point(const std::string &str)
{
using namespace std;
using namespace std::chrono;
int yyyy, mm, dd, HH, MM, SS, fff;
char scanf_format[] = "%4d.%2d.%2d-%2d.%2d.%2d.%3d";
sscanf(str.c_str(), scanf_format, &yyyy, &mm, &dd, &HH, &MM, &SS, &fff);
tm ttm = tm();
ttm.tm_year = yyyy - 1900; // Year since 1900
ttm.tm_mon = mm - 1; // Month since January
ttm.tm_mday = dd; // Day of the month [1-31]
ttm.tm_hour = HH; // Hour of the day [00-23]
ttm.tm_min = MM;
ttm.tm_sec = SS;
time_t ttime_t = mktime(&ttm);
system_clock::time_point time_point_result = std::chrono::system_clock::from_time_t(ttime_t);
time_point_result += std::chrono::milliseconds(fff);
return time_point_result;
}
std::string time_point_to_string(std::chrono::system_clock::time_point &tp)
{
using namespace std;
using namespace std::chrono;
auto ttime_t = system_clock::to_time_t(tp);
auto tp_sec = system_clock::from_time_t(ttime_t);
milliseconds ms = duration_cast<milliseconds>(tp - tp_sec);
std::tm * ttm = localtime(&ttime_t);
char date_time_format[] = "%Y.%m.%d-%H.%M.%S";
char time_str[] = "yyyy.mm.dd.HH-MM.SS.fff";
strftime(time_str, strlen(time_str), date_time_format, ttm);
string result(time_str);
result.append(".");
result.append(to_string(ms.count()));
return result;
}
I would have put this in a comment on the accepted answer, since that's where it belongs, but I can't. So, just in case anyone gets unreliable results, this could be why.
Be careful of the accepted answer, it fails if the time_point is before the epoch.
This line of code:
std::size_t fractional_seconds = ms.count() % 1000;
will yield unexpected values if ms.count() is negative (since size_t is not meant to hold negative values).
In my case I use chrono and c function localtime_r which is thread-safe (in opposition to std::localtime).
#include <iostream>
#include <chrono>
#include <ctime>
#include <time.h>
#include <iomanip>
int main() {
std::chrono::system_clock::time_point now = std::chrono::system_clock::now();
std::time_t currentTime = std::chrono::system_clock::to_time_t(now);
std::chrono::milliseconds now2 = std::chrono::duration_cast<std::chrono::milliseconds>(now.time_since_epoch());
struct tm currentLocalTime;
localtime_r(¤tTime, ¤tLocalTime);
char timeBuffer[80];
std::size_t charCount { std::strftime( timeBuffer, 80,
"%b %d %T",
¤tLocalTime)
};
if (charCount == 0) return -1;
std::cout << timeBuffer << "." << std::setfill('0') << std::setw(3) << now2.count() % 1000 << std::endl;
return 0;
}
If you are to format a system_clock::time_point in the format of numpy datetime64, you could use:
std::string format_time_point(system_clock::time_point point)
{
static_assert(system_clock::time_point::period::den == 1000000000 && system_clock::time_point::period::num == 1);
std::string out(29, '0');
char* buf = &out[0];
std::time_t now_c = system_clock::to_time_t(point);
std::strftime(buf, 21, "%Y-%m-%dT%H:%M:%S.", std::localtime(&now_c));
sprintf(buf+20, "%09ld", point.time_since_epoch().count() % 1000000000);
return out;
}
sample output: 2019-11-19T17:59:58.425802666
Is there a cross-platform way to get the current date and time in C++?
Since 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"
<< std::endl;
}
This should print something like this:
finished computation at Mon Oct 2 00:59:08 2017
elapsed time: 1.88232s
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";
}
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
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);
New answer for an old question:
The question does not specify in what timezone. There are two reasonable possibilities:
In UTC.
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>.
#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
}
As I write this, partial implementations are just beginning to emerge on some platforms.
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;
}
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.
(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();
#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;
}
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
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
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
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
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;
}
PS: Visit this site for more information.
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;
}
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
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;
}
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;
}
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.
http://www.cplusplus.com/reference/ctime/strftime/
This built-in seems to offer a reasonable set of options.
localtime_s() version:
#include <stdio.h>
#include <time.h>
int main ()
{
time_t current_time;
struct tm local_time;
time ( ¤t_time );
localtime_s(&local_time, ¤t_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;
}
#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;
}
Here is the non-deprecated modern C++ solution for getting a timestamp as a std::string for use with e.g. filenames:
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();
}
You could use boost and chrono library:
#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)));
}
#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)
}
I needed a way to insert current date-time at every update of a list.
This seems to work well, simply.
#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";
}