C Exercises: Print the date and time before 24 months

Last update on August 06 2025 12:54:04 (UTC/GMT +8 hours)

8. Date and Time 24 Months Ago

Write a program in C to print the date and time before 24 months.

Sample Solution:

C Code:

// Define _POSIX_C_SOURCE to enable specific POSIX features
#define _POSIX_C_SOURCE 200112L 

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

int main(void)
{
    // Set the timezone environment variable to "Asia/Calcutta"
    setenv("TZ", "/usr/share/zoneinfo/Asia/Calcutta", 1);   

    // Get the current local time and store it in a tm structure
    struct tm tm = *localtime(&(time_t){time(NULL)});

    // Print today's date and check if Daylight Saving Time (DST) is in effect
    printf("\nToday is :          %s", asctime(&tm));
    printf("(DST is %s)\n", tm.tm_isdst ? "in effect" : "not in effect");

    // Subtract 24 months from the month value of the stored time structure
    tm.tm_mon -= 24;  

    // Normalize the modified time structure using mktime
    mktime(&tm);       

    // Print the date from 24 months ago and check if DST was in effect
    printf("\n24 months ago the date was : %s", asctime(&tm));
    printf("(DST was %s)\n\n", tm.tm_isdst ? "in effect" : "not in effect");
}

Output:

Today is :          Thu Aug  3 17:27:16 2017                                                                                  
(DST is not in effect)                                                                                                        
                                                                                                                              
24 months ago the date was : Mon Aug  3 17:27:16 2015                                                                         
(DST was not in effect)

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

Flowchart:

Flowchart: Print the date and time before 24 months

For more Practice: Solve these Related Problems:

Write a C program to compute and print the date and time exactly 24 months before the current date, accounting for leap years.
Write a C program to display the current date and time, then subtract 24 months and print the adjusted date in a custom format.
Write a C program to calculate the date and time 24 months ago using calendar arithmetic and display both the original and resulting dates.
Write a C program to subtract 24 months from the current time, handle day-of-month overflow, and then output the final date and time.

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C Programming Code Editor:

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