C++ Tutorial/Data Types/time

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Convert now to tm struct for local timezone

#include <iostream>
#include <ctime>
#include <cstdlib>
using namespace std;
int main( )
{
  // 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;
}
The local date and time is: Mon Apr 23 13:17:32 2007

Convert now to tm struct for UTC

#include <iostream>
#include <ctime>
#include <cstdlib>
using namespace std;
int main( )
{
  // Current date/time based on current system
  time_t now = time(0);
   // 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;
  }
}
The UTC date and time is: Mon Apr 23 20:17:33 2007

%c specifies the standard time and date pattern

#include <iostream>
#include <locale>
#include <cstring>
#include <ctime>
using namespace std;
int main()
{
  // Obtain the current system time.
  time_t t = time(NULL);
  tm *cur_time = localtime(&t);
  // Create US and German locales.
  locale usloc("English_US");
  locale gloc("German_Germany");
  // %c specifies the standard time and date pattern.
  char *std_pat = "%c";
  char *std_pat_end = std_pat + strlen(std_pat);
  return 0;
}

custom pattern displays hours and minutes followed by the date

#include <iostream>
#include <locale>
#include <cstring>
#include <ctime>
using namespace std;
int main()
{
  // Obtain the current system time.
  time_t t = time(NULL);
  tm *cur_time = localtime(&t);
  // Create US and German locales.
  locale usloc("English_US");
  locale gloc("German_Germany");
  // custom pattern displays hours and minutes followed by the date.
  char *custom_pat = "%A %B %d, %Y %H:%M";
  char *custom_pat_end = custom_pat + strlen(custom_pat);
  return 0;
}

Demonstrating the use of the ctime( ) function.

#include <time.h>
#include <iostream>
using namespace std;
time_t longtime;
int main( )
{
 time(&longtime);
 cout << "The time and date are " <<
         ctime(&longtime) << "\n";
 return (0);
}

Demonstrating the use of the gmtime( ) and asctime( ) functions.

#include <time.h>
#include <stdio.h>
int main( )
{
 struct tm *date_time;
 time_t timer;
 time(&timer);
 date_time=gmtime(&timer);
 printf("%.19s\n",asctime(date_time));
 return (0);
}

Demonstrating the use of the localtime( ) and asctime( ) functions.

#include <time.h>
#include <stdio.h>
struct tm *date_time;
time_t timer;
int main( )
{
 time(&timer);
 date_time=localtime(&timer);
 printf("The present date and time is: %s\n",
 asctime(date_time));
 return (0);
}

Displays the current date and time

#include <iostream>
using std::cout;
#include <ctime>
using std::time_t;
using std::time;
using std::localtime;
using std::asctime;
int main()
{
   time_t currentTime;
   
   time( &currentTime );
   
   cout << asctime( localtime( &currentTime ) );
   return 0;
}
Sun Apr 29 10:56:45 2007

Set the locale to Germany and get the time_put facet for Germany

#include <iostream>
#include <locale>
#include <cstring>
#include <ctime>
using namespace std;
int main()
{
  // Obtain the current system time.
  time_t t = time(NULL);
  tm *cur_time = localtime(&t);
  // Create US and German locales.
  locale usloc("English_US");
  locale gloc("German_Germany");
  // Set the locale to Germany and get the time_put facet for Germany.
  cout.imbue(gloc);
  const time_put<char> &g_time = use_facet<time_put<char> >(cout.getloc());
  return 0;
}

Set the locale to Germany, Show standard time and date string

#include <iostream>
#include <ctime>
#include <clocale>
using namespace std;
int main() {
  char str[64];
  // Set the locale to Germany.
  setlocale(LC_ALL, "German_Germany");
  // Get the current system time.
  time_t t = time(NULL);
  // Show standard time and date string.
  strftime(str, 64, "%c", localtime(&t));
  cout << "Standard format: " << str << endl;
  // Show a custom time and date string.
  strftime(str, 64, "%A, %B %Y %I:%M %p", localtime(&t));
  cout << "Custom format: " << str << endl;
  return 0;
}

Set the locale to US and get the time_put facet for US

#include <iostream>
#include <locale>
#include <cstring>
#include <ctime>
using namespace std;
int main()
{
  // Obtain the current system time.
  time_t t = time(NULL);
  tm *cur_time = localtime(&t);
  // Create US and German locales.
  locale usloc("English_US");
  locale gloc("German_Germany");
  // Set the locale to US and get the time_put facet for US.
  cout.imbue(usloc);
  const time_put<char> &us_time = use_facet<time_put<char> >(cout.getloc());

  return 0;
}

Show a custom time and date string

#include <iostream>
#include <ctime>
using namespace std;
int main() {
  char str[64];
  // Get the current system time.
  time_t t = time(NULL);
  // Show a custom time and date string.
  strftime(str, 64, "%A, %B %d %Y %I:%M %p", localtime(&t));
  cout << "Custom format: " << str << endl;
  return 0;
}

Show standard time and date string

#include <iostream>
#include <ctime>
using namespace std;
int main() {
  char str[64];
  // Get the current system time.
  time_t t = time(NULL);
  // Show standard time and date string.
  strftime(str, 64, "%c", localtime(&t));
  cout << "Standard format: " << str << endl;
  return 0;
}

The strftime( ) Format Specifiers

Command           Replaced By
%a                Abbreviated weekday name
%A                Full weekday name
%b                Abbreviated month name
%B                Full month name
%c                Standard date and time string
%d                Day of month as a decimal (1-31)
%H                Hour (0-23)
%I                Hour (1-12)
%j                Day of year as a decimal (1-366)
%m                Month as decimal (1-12)
%M                Minute as decimal (0-59)
%p                Locale"s equivalent of AM or PM
%S                Second as decimal (0-61)
%U                Week of year, Sunday being first day (0-53)
%w                Weekday as a decimal (0-6, Sunday being 0)
%W                Week of year, Monday being first day (0-53)
%x                Standard date string
%X                Standard time string
%y                Year in decimal without century (0-99)
%Y                Year including century as decimal
%Z                Time zone name
%%                The percent sign

use of the strftime( ) function.

#include <time.h>
#include <stdio.h>
int main( )
{
 struct tm *date_time;
 time_t timer;
 char str[80];
 time(&timer);
 date_time=localtime(&timer);
 strftime(str,80,"It is %X on %A, %x",
          date_time);
 printf("%s\n",str);
 return (0);
}
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