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Implementation in C++
Complexity Analysis
Key Takeaways
Last Updated: Mar 27, 2024

Program to convert 24 hour time to 12 hour time

Author Urwashi Priya
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Ashwin Goyal
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This blog will discuss how to write a Program to convert 24 hour time to 12 hour time.

We are given a time in 24-hour format and we need to convert it into 12-hour format.



In 24 hour time, after 12 noon, 13:00 is said to be 1p.m similarly 14:00 as 2 pm and so on.

You can also read about dynamic array in c.

Also see: C Static Function


The approach to write a Program to convert 24 hour time to 12 hour time is to first get hours, then calculate whether the time is in AM or PM. We need to calculate whether the time is from 0 to 12 or from 12 to 24. Both the cases should be handled separately and then displayed.

Time Complexity for writing a program to convert 24 hour time to 12-hour time = O(1), since constant time is taken.

Till now, I assume you must have got the basic idea of what has been asked in the problem statement. So, I strongly recommend you first give it a try.

try here


procedure convert(string str):
1.   h1 = (int)str[0] - '0'
2.   h2 = (int)str[1] - '0'
3.   hh = h1 * 10 + h2
4.   if (hh < 12):
           Meridien = "AM" 
           Meridien = "PM";
5.   hh %= 12
6.   if (hh == 0):
          cout << "12"
          for (i = 2 to 8):
                  cout << str[i]  
7.   else 
          cout << hh
          for (i = 2 to 8):
                  cout << str[i]
8.   Print meridien
end procedure

Also read,  Tribonacci Series

Implementation in C++

#include <bits/stdc++.h>
using namespace std;

// Function to convert 24-hour time to 12 hour
void convert(string str)
	// Getting Hours
	int h1 = (int)str[0] - '0';
	int h2 = (int)str[1] - '0';

	int hh = h1 * 10 + h2;

	// Finding out AM or PM
	string Meridien;
	if (hh < 12) {
		Meridien = "AM";
		Meridien = "PM";

	hh %= 12;

	// Handling 00 and 12 case separately
	if (hh == 0) {
		cout << "12";

		// Printing minutes and seconds
		for (int i = 2; i < 8; ++i) {
			cout << str[i];
	else {
		cout << hh;
		// Printing minutes and seconds
		for (int i = 2; i < 8; ++i) {
			cout << str[i];

	// After time print am or pm
	cout << " " << Meridien << '\n';

int main()
    // enter in 24 hour format
    string str;
	return 0;



Sample Input:
Sample Output:
8:25:30 PM

You can implement code by yourself with the help of the online c compiler.

Complexity Analysis

Time Complexity: O(1), The constant time is taken to convert time from 24-hour format to 12-hour format.

Space complexity: O(1), since no extra variable was used. 

Also see, Short int in C Programming

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  1. What are the different data types used in C++?
    The different data types in c++ are int for integers, float and double for decimals, char for characters, bool for boolean ,etc.
  2.  What is the 24-hour time format?
    The 24-hour time format includes time ranging from 0 to 24. After 12 noon, 13:00 is referred to as 1 pm, 14:00 is referred to as 2 pm and so on.
  3. What is a decision-making statement?
    A decision-making statement is used for conditional statements. It includes an if-else statement.

Key Takeaways

This article taught us how to write a Program to convert 24 hour time to 12 hour time.

We hope you could take away critical techniques like analysing problems by walking over the execution of the steps and finding out the pattern followed in most basic problems.

Also read reverse a number.

Now, we recommend you practice problem sets based on simple loops to master your fundamentals. You can get a wide range of questions similar to this on Coding Ninjas Studio

It's not the end. Must solve the problem of similar types. 

Happy Coding.

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