Question

How to format a date using different formats in C

Answer 1

#include <stdio.h>
#include <time.h>

/*
time() → gets current time as seconds since 1970. 
localtime() → converts it into a struct tm with fields like year, month, day, hour. 
strftime() → formats the date/time using format specifiers. 

Common strftime format specifiers:
%Y — 4‑digit year (e.g., 2026)
%m — month (01–12)
%d — day of month (01–31)
%H — hour (00–23)
%M — minute (00–59)
%S — second (00–59)
%A — full weekday name
%B — full month name
*/

int main() {
    time_t now = time(NULL);          // current timestamp
    struct tm *t = localtime(&now);   // break into components

    char buffer[128] = "";
    strftime(buffer, sizeof(buffer), "%d-%m-%Y %H:%M:%S", t);
    printf("Formatted time: %s\n", buffer);
    
    strftime(buffer, sizeof(buffer), "%Y-%m-%d", t);      
    printf("Formatted time: %s\n", buffer);
    
    strftime(buffer, sizeof(buffer), "%d/%m/%y", t);       
    printf("Formatted time: %s\n", buffer);
    
    strftime(buffer, sizeof(buffer), "%A, %B %d, %Y", t);  
    printf("Formatted time: %s\n", buffer);
    
    strftime(buffer, sizeof(buffer), "%I:%M %p", t);       
    printf("Formatted time: %s\n", buffer);

    return 0;
}



/*
run:

Formatted time: 20-05-2026 08:58:26
Formatted time: 2026-05-20
Formatted time: 20/05/26
Formatted time: Wednesday, May 20, 2026
Formatted time: 08:58 AM

*/

 

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Answer 2

#include <stdio.h>
#include <time.h>

/*
time() → gets current time as seconds since 1970. 
localtime() → converts it into a struct tm with fields like year, month, day, hour. 
strftime() → formats the date/time using format specifiers. 

format specifier:
%Y — 4‑digit year
%m — month (01–12)
%d — day of month
%H — hour (00–23)
%I — hour (01–12)
%M — minutes
%S — seconds
%A — full weekday name
%B — full month name
%c — locale’s default date/time
%j — day of year (001–366)
%W — week number (Mon-start)
%U — week number (Sun-start)
*/

#include <stdio.h>
#include <time.h>

int main() {
    time_t now = time(NULL);          // Get current timestamp
    struct tm *t = localtime(&now);   // Convert to local time components

    char buf[128];

    // --- Basic numeric formats ---
    strftime(buf, sizeof(buf), "%Y-%m-%d", t);
    printf("ISO format (YYYY-MM-DD): %s\n", buf);

    strftime(buf, sizeof(buf), "%d/%m/%Y", t);
    printf("European format (DD/MM/YYYY): %s\n", buf);

    strftime(buf, sizeof(buf), "%m-%d-%Y", t);
    printf("US format (MM-DD-YYYY): %s\n", buf);

    // --- Time formats ---
    strftime(buf, sizeof(buf), "%H:%M:%S", t);
    printf("24-hour time: %s\n", buf);

    strftime(buf, sizeof(buf), "%I:%M:%S %p", t);
    printf("12-hour time: %s\n", buf);

    // --- Full date with names ---
    strftime(buf, sizeof(buf), "%A, %B %d, %Y", t);
    printf("Full weekday + month name: %s\n", buf);

    strftime(buf, sizeof(buf), "%a, %b %d", t);
    printf("Short weekday + month name: %s\n", buf);

    // --- Combined date/time ---
    strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S", t);
    printf("Full timestamp: %s\n", buf);

    strftime(buf, sizeof(buf), "%c", t);
    printf("Locale default date/time: %s\n", buf);

    // --- Special formats ---
    strftime(buf, sizeof(buf), "Day of year: %j", t);
    printf("%s\n", buf);

    strftime(buf, sizeof(buf), "Week number (Mon-start): %W", t);
    printf("%s\n", buf);

    strftime(buf, sizeof(buf), "Week number (Sun-start): %U", t);
    printf("%s\n", buf);

    return 0;
}



/*
run:

ISO format (YYYY-MM-DD): 2026-05-20
European format (DD/MM/YYYY): 20/05/2026
US format (MM-DD-YYYY): 05-20-2026
24-hour time: 09:04:58
12-hour time: 09:04:58 AM
Full weekday + month name: Wednesday, May 20, 2026
Short weekday + month name: Wed, May 20
Full timestamp: 2026-05-20 09:04:58
Locale default date/time: Wed May 20 09:04:58 2026
Day of year: 140
Week number (Mon-start): 20
Week number (Sun-start): 20

*/

 

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