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Program to convert time from 12 hour to 24 hour format
  • Difficulty Level : Easy
  • Last Updated : 22 Oct, 2020

Given a time in 12-hour AM/PM format, convert it to military (24-hour) time. 
Note: Midnight is 12:00:00 AM on a 12-hour clock and 00:00:00 on a 24-hour clock. Noon is 12:00:00 PM on 12-hour clock and 12:00:00 on 24-hour clock

Examples:

Input : A single string containing a time in 12-hour 
clock format(hh:mm:ss AM or hh:mm:ss PM
        where 01 <= hh <= 12 or 01 <= mm,ss <= 59 
Output :Convert and print the given time in 24-hour format,
where 00 <= hh <= 23

Input : 07:05:45PM
Output : 19:05:45

C++

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// C++ program to convert 12 hour to 24 hour
// format
#include<iostream>
using namespace std;
 
void print24(string str)
{
    // Get hours
    int h1 = (int)str[1] - '0';
    int h2 = (int)str[0] - '0';
    int hh = (h2 * 10 + h1 % 10);
 
    // If time is in "AM"
    if (str[8] == 'A')
    {
        if (hh == 12)
        {
            cout << "00";
            for (int i=2; i <= 7; i++)
                cout << str[i];
        }
        else
        {
            for (int i=0; i <= 7; i++)
                cout << str[i];
        }
    }
 
    // If time is in "PM"
    else
    {
        if (hh == 12)
        {
            cout << "12";
            for (int i=2; i <= 7; i++)
                cout << str[i];
        }
        else
        {
            hh = hh + 12;
            cout << hh;
            for (int i=2; i <= 7; i++)
                cout << str[i];
        }
    }
}
 
// Driver code
int main()
{
   string str = "07:05:45PM";
   print24(str);
   return 0;
}

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Java

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// Java program to convert 12 hour
// format to  24 hour format
class GFG
{
static void print24(String str)
{
    // Get hours
    int h1 = (int)str.charAt(1) - '0';
    int h2 = (int)str.charAt(0) - '0';
    int hh = (h2 * 10 + h1 % 10);
 
    // If time is in "AM"
    if (str.charAt(8) == 'A')
    {
        if (hh == 12)
        {
            System.out.print("00");
            for (int i = 2; i <= 7; i++)
                System.out.print(str.charAt(i));
        }
        else
        {
            for (int i = 0; i <= 7; i++)
                System.out.print(str.charAt(i));
        }
    }
 
    // If time is in "PM"
    else
    {
        if (hh == 12)
        {
            System.out.print("12");
            for (int i = 2; i <= 7; i++)
                System.out.print(str.charAt(i));
        }
        else
        {
            hh = hh + 12;
            System.out.print(hh);
            for (int i = 2; i <= 7; i++)
                System.out.print(str.charAt(i));
        }
    }
}
 
// Driver code
public static void main (String[] args)
{
    String str = "07:05:45PM";
    print24(str);
}
}
 
// This code is contributed by Anant Agarwal.

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Python3

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# Python3 program to convert 12
# hour to 24 hour format
def print24(s):
 
    # Get hours
    h1 = ord(s[1]) - ord('0')
    h2 = ord(s[0]) - ord('0')
    hh = (h2 * 10 + h1 % 10)
  
    # If time is in "AM"
    if (s[8] == 'A'):
        if (hh == 12):
            print('00', end = '')
             
            for i in range(2, 8):
                print(s[i], end = '')
 
        else:
            for i in range(0, 8):
                print(s[i], end = '')
  
    # If time is in "PM"
    else:
        if (hh == 12):
            print("12", end = '')
             
            for i in range(2, 8):
                print(s[i], end = '')
         
        else:
            hh = hh + 12;
            print(hh, end = '')
             
            for i in range(2, 8):
                print(s[i], end = '')
             
# Driver code          
if __name__=="__main__":
 
   s = "07:05:45PM"
    
   print24(s)
    
# This code is contributed by rutvik_56

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C#

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// C# program to convert 12 hour
// format to 24 hour format
using System;
 
class GFG
{
     
static void print24(String str)
{
    // Get hours
    int h1 = (int)str[1] - '0';
    int h2 = (int)str[0] - '0';
    int hh = (h2 * 10 + h1 % 10);
 
    // If time is in "AM"
    if (str[8] == 'A')
    {
        if (hh == 12)
        {
            Console.Write("00");
            for (int i = 2; i <= 7; i++)
                Console.Write(str[i]);
        }
        else
        {
            for (int i = 0; i <= 7; i++)
                Console.Write(str[i]);
        }
    }
 
    // If time is in "PM"
    else
    {
        if (hh == 12)
        {
            Console.Write("12");
            for (int i = 2; i <= 7; i++)
                Console.Write(str[i]);
        }
        else
        {
            hh = hh + 12;
            Console.Write(hh);
            for (int i = 2; i <= 7; i++)
                Console.Write(str[i]);
        }
    }
}
 
// Driver code
public static void Main(String[] args)
{
    String str = "07:05:45PM";
    print24(str);
}
}
 
// This code is contributed by Rajput-Ji

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Output: 

19:05:45


This article is contributed by Rahul singh (Nit kkr). If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
 

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