Write a C program for time conversions using if and elseif statements

In this tutorial, we will learn how to convert time from 24-hour format (also known as military time) to 12-hour format using C programming with if and else if statements. The 24-hour format uses hours from 00 to 23, while the 12-hour format uses hours from 1 to 12 with AM/PM indicators.

Syntax

if (condition1) {
    // statements
} else if (condition2) {
    // statements
} else {
    // statements
}

Algorithm

Start:
Step 1: Enter time in 24 hr format (hour:minute)
Step 2: Check the conditions using if-else if statements:
        i. If (hour == 0)
           Display as 12:mm AM (midnight hour)
        ii. Else if (hour < 12)
            Display as hour:mm AM (morning hours)
        iii. Else if (hour == 12)
             Display as 12:mm PM (noon hour)
        iv. Else
            Display as (hour % 12):mm PM (afternoon/evening)
Stop

Example Program

The following program reads time in 24-hour format and converts it to 12-hour format using conditional statements −

#include <stdio.h>

int main() {
    int hr, min;
    
    printf("Enter the time in 24 hour format (HH:MM): ");
    scanf("%d:%d", &hr, &min);
    
    printf("The 12 hour format time: ");
    
    if (hr == 0) {
        printf("12:%.2d AM<br>", min);
    }
    else if (hr < 12) {
        printf("%d:%.2d AM<br>", hr, min);
    }
    else if (hr == 12) {
        printf("%d:%.2d PM<br>", hr, min);
    }
    else {
        printf("%d:%.2d PM<br>", hr % 12, min);
    }
    
    return 0;
}

Output

Enter the time in 24 hour format (HH:MM): 22:37
The 12 hour format time: 10:37 PM

How It Works

• Hour 0 (00:xx): Represents midnight, displayed as 12:xx AM
• Hours 1-11 (01:xx to 11:xx): Morning hours, displayed as-is with AM
• Hour 12 (12:xx): Noon hour, displayed as 12:xx PM
• Hours 13-23 (13:xx to 23:xx): Afternoon/evening hours, subtract 12 and display with PM

Key Points

• The %.2d format specifier ensures minutes are displayed with leading zeros when less than 10
• The modulo operator % is used to convert hours greater than 12 to 12-hour format
• Special handling is required for hour 0 (midnight) and hour 12 (noon)

Conclusion

Time conversion from 24-hour to 12-hour format using if-else if statements is straightforward. The key is handling special cases like midnight (00:xx) and noon (12:xx) correctly while applying the modulo operation for afternoon hours.