Change time from 24 hours format to 12 hours format

In this article, we have explained how to change time from 24 hours format (HH:MM) to 12 hours format (HH:MM + AM or PM) and implemented the approach in C Programming Language.

Table of contents:

1. Problem Statement
2. Approach to change 24 hours format to 12 hours format
3. Implementation in C
4. Output

Problem Statement

In this problem, we have to write a program in C programming language that takes a time in 24 hours format as input and gives the output time in 12 hours format.

For example, if the input time is 23:15 (HH:MM format), then output time will be 11:15 PM.

Similarly, if the input time is 10:49 (in 24 hours HH:MM format), the output time will be 10:49 AM.

Approach to change 24 hours format to 12 hours format

The approach/ steps to change the time format from 24 hours format to 12 hours format is as follows:

1. The time is 24 hours format is of the form HH and MM where HH is hours from 00 to 24 and minutes MM is from 00 to 59.
2. We assume the input time is a valid time.
3. If HH is < 12, then the output is same as input with "am" appended to it.
4. If HH is >= 12, then HH is modified as HH-12 and the new HH and original MM is the output with "pm" appended to it.

Implementation in C

Following is the implementation in C Programming Language:

#include<stdio.h>
int main()
{
	int a,b,c;
	printf("Enter a time in 24 hours format=");
	scanf("%d%d",&a,&b);
	if(a<12)
	{
		printf("%d:%dam",a,b);
	}
	else
	{
		c=a-12;
		printf("%d:%dpm",c,b);
	}
	
	return 0;
}

Output

Following is the command to compile and run the program:

gcc opengenus.c
./a.out

Sample input is as follows:

21
34

The output of the above program is:

Enter a time in 24 hours format=9:34pm

Another sample input is as follows:

11
45

The output for the above input will be as follows:

Enter a time in 24 hours format=11:45am

With this article at OpenGenus, you must have the complete idea of how to change time from 24 hours format to 12 hours format and write a C program for it.