C - Date and Time
=================
    
Public Domain
********************************************************************************
### strftime - format date and time
    
    #include <stdio.h>
    #include <stdlib.h>
    #include <time.h>
    
    int main()
    {
        time_t t;
        struct tm *tm;
        char str[200];
    
        t = time(NULL);
    
        tm = localtime(&t);
            if (tm == NULL) {
                    perror("localtime");
                    exit(EXIT_FAILURE);
            }
    
        if (strftime(str, sizeof(str), "%a %b %e %T %Z %Y", tm) == 0) {
                fprintf(stderr, "strftime returned 0");
                exit(EXIT_FAILURE);
        }
        printf("strftime is %s\n", str);
    
        tm = localtime(&t);
        printf("\n--Local Time--\n");
        printf("tm->tm_sec: %d\n", tm->tm_sec);
        printf("tm->tm_min: %d\n", tm->tm_min);
        printf("tm->tm_hour: %d\n", tm->tm_hour);
        printf("tm->tm_mday: %d\n", tm->tm_mday);
        printf("tm->tm_mon: %d\n", tm->tm_mon);
        printf("tm->tm_year: %d\n", tm->tm_year);
        printf("tm->tm_wday: %d\n", tm->tm_wday);
        printf("tm->tm_yday: %d\n", tm->tm_yday);
        printf("tm->tm_isdst: %d\n", tm->tm_isdst);
    
        tm = gmtime(&t);
        printf("\n--Greenwich Time--\n");
        printf("tm->tm_sec: %d\n", tm->tm_sec);
        printf("tm->tm_min: %d\n", tm->tm_min);
        printf("tm->tm_hour: %d\n", tm->tm_hour);
        printf("tm->tm_mday: %d\n", tm->tm_mday);
        printf("tm->tm_mon: %d\n", tm->tm_mon);
        printf("tm->tm_year: %d\n", tm->tm_year);
        printf("tm->tm_wday: %d\n", tm->tm_wday);
        printf("tm->tm_yday: %d\n", tm->tm_yday);
        printf("tm->tm_isdst: %d\n", tm->tm_isdst);
    
        return 0;
    }

Output

        strftime is Thu Jan 16 00:40:36 IRST 2014

        --Local Time--
        tm->tm_sec: 36
        tm->tm_min: 40
        tm->tm_hour: 0
        tm->tm_mday: 16
        tm->tm_mon: 0
        tm->tm_year: 114
        tm->tm_wday: 4
        tm->tm_yday: 15
        tm->tm_isdst: 0

        --Greenwich Time--
        tm->tm_sec: 36
        tm->tm_min: 10
        tm->tm_hour: 21
        tm->tm_mday: 15
        tm->tm_mon: 0
        tm->tm_year: 114
        tm->tm_wday: 3
        tm->tm_yday: 14
        tm->tm_isdst: 0

********************************************************************************
### strptime - convert a string representation of time to a time tm structure
    
    
    #define _XOPEN_SOURCE
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <time.h>
    
    int main()
    {
        struct tm tm;
        char str[255];
    
        memset(&tm, 0, sizeof(struct tm));
        strptime("2014-01-16 00:01:54", "%Y-%m-%d %H:%M:%S", &tm);
        strftime(str, sizeof(str), "%d %b %Y %H:%M", &tm);
        puts(str);
        exit(EXIT_SUCCESS);
    }

Output

    16 Jan 2014 00:01
    
********************************************************************************
### mktime - converts a broken-down time structure, expressed as local time, to calendar time representation
    
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <time.h>
    
    int main()
    {
        struct tm *tm = malloc(sizeof(struct tm));
        time_t t;
        char str[200];
    
        memset((void *)tm, 0, sizeof(struct tm));
    
        tm->tm_sec   = 13;
        tm->tm_min   = 13;
        tm->tm_hour  = 13;
        tm->tm_mday  = 10;
        tm->tm_mon   = 0;
        tm->tm_year  = 100;
        tm->tm_isdst = 0; 
    
        t = mktime(tm);
    
        tm = localtime(&t);
        strftime(str, sizeof(str), "%F %T", tm);
        printf("localtime is %s\n", str);
    
        tm = gmtime(&t);
        strftime(str, sizeof(str), "%F %T", tm);
        printf("greenwich is %s\n", str);
    
        return 0;
    }

Output

    localtime is 2000-01-10 13:13:13
    greenwich is 2000-01-10 09:43:13

    
********************************************************************************
### gettimeofday 

    #include <stdio.h>
    #include <stdlib.h>
    #include <sys/time.h>
    #include <time.h>

    int main()
    {
        struct timeval tv;
        struct tm *tm;
        char str[200];

        if(gettimeofday(&tv, NULL) == -1 ) {
                perror("gettimeofday");
                exit(EXIT_FAILURE);
        }
        printf("tv->tv_sec: %d\n", tv.tv_sec);
        printf("tv->tv_usec: %d\n", tv.tv_usec);

        strftime(str, sizeof(str), "%a %b %e %T %Z %Y", localtime(&tv.tv_sec));
        printf("strftime is %s\n", str);

        exit(EXIT_SUCCESS);
    }

Output

    tv->tv_sec: 1389879829
    tv->tv_usec: 314898
    strftime is Thu Jan 16 17:13:49 IRST 2014

********************************************************************************
_BY: Pejman Moghadam_  
_TAG: c, date, time, strftime_  
_DATE: 2014-01-16 17:14:22_