C Exercises: Convert a time_t object to calendar time expressed as local time

Last update on March 20 2025 12:31:31 (UTC/GMT +8 hours)

7. time_t to Local Calendar Time

Write a program in C to convert a time_t object to calendar time expressed as local time.

Sample Solution:

C Code:

#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
#include <time.h>

int main(void)
{
    // Get current time in seconds since epoch
    time_t t = time(NULL);

    // Print the calendar time expressed as local time and UTC time
    printf("\nThe calendar time expressed as a local Time is :");
    printf("\nUTC:   %s", asctime(gmtime(&t))); // Convert and print UTC time
    printf("local: %s\n", asctime(localtime(&t))); // Convert and print local time

#ifdef __STDC_LIB_EXT1__
    // Using secure versions of functions available in C11
    struct tm buf;
    char str[26];

    // Convert and print UTC time using secure version of functions
    asctime_s(str, sizeof str, gmtime_s(&t, &buf));
    printf("UTC:   %s", str);

    // Convert and print local time using secure version of functions
    asctime_s(str, sizeof str, localtime_s(&t, &buf));
    printf("local: %s", str);
#endif
}

Output:

The calendar time expressed as a local Time is :
UTC:   Thu Aug 03 11:15:59 2017
local: Thu Aug 03 16:45:59 2017

N.B.: The result may varry for your current system date and time.

Flowchart:

For more Practice: Solve these Related Problems:

• Write a C program to convert a time_t object to local calendar time and print it in a 12-hour and 24-hour format.
• Write a C program to format a time_t object into local time and include the day of the week in the output.
• Write a C program to convert a time_t object to local time and display the result with leading zeros for hours, minutes, and seconds.
• Write a C program to show the local calendar time from a time_t object and then compare it with the current system time.

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