Java Date – Convert 12 hour format to 24 hour format and vice versa

In this tutorial we will see how to convert 12 hour format to 24 hour format and 24 hour format to 12 hour format in Java.

Java – Convert 12 Hour data time format to 24 hour date time format

We can change the pattern in the SimpleDateFormat for the conversion. The pattern dd/MM/yyyy hh:mm:ss aa is used for the 12 hour format and the pattern MM-dd-yyyy HH:mm:ss is used for the 24 hour format. In this program we are changing the format of the date by changing the patterns and formatting the input date.

Input/Output of the Program:
Input date and time: 23/12/2014 12:22:12 PM (12 hour format)
Output date and time: 12-23-2014 22:22:12 (24 hour format)

import java.text.SimpleDateFormat;
import java.text.DateFormat;
import java.util.Date;
import java.text.ParseException;
class DateTimeFormatDemo
{
   public static void main(String[] args)
   {
      String input = "23/12/2014 10:22:12 PM";
      //Format of the date defined in the input String
      DateFormat df = new SimpleDateFormat("dd/MM/yyyy hh:mm:ss aa");
      //Desired format: 24 hour format: Change the pattern as per the need
      DateFormat outputformat = new SimpleDateFormat("MM-dd-yyyy HH:mm:ss");
      Date date = null;
      String output = null;
      try{
         //Converting the input String to Date
    	 date= df.parse(input);
         //Changing the format of date and storing it in String
    	 output = outputformat.format(date);
         //Displaying the date
    	 System.out.println(output);
      }catch(ParseException pe){
         pe.printStackTrace();
       }
   }
}

Output:

12-23-2014 22:22:12

Java – Convert 24 Hour format to 12 hour format

In this example we are doing the opposite of what we have done in the above example. Here we are converting the 24 hour format of input date into a 12 hour format.

Input/Output of the program:
Input date and time: 15/02/2014 22:22:12(24 hour format dd/MM/yyyy HH:mm:ss)
Output date and time: 2014-02-15 10:22:12 PM (12 hour format yyyy-MM-dd hh:mm:ss aa)

import java.text.SimpleDateFormat;
import java.text.DateFormat;
import java.util.Date;
import java.text.ParseException;
class Example2
{
   public static void main(String[] args)
   {
       //Input date in String format
       String input = "15/02/2014 22:22:12";
       //Date/time pattern of input date
       DateFormat df = new SimpleDateFormat("dd/MM/yyyy HH:mm:ss");
       //Date/time pattern of desired output date
       DateFormat outputformat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss aa");
       Date date = null;
       String output = null;
       try{
          //Conversion of input String to date
    	  date= df.parse(input);
          //old date format to new date format
    	  output = outputformat.format(date);
    	  System.out.println(output);
    	}catch(ParseException pe){
    	    pe.printStackTrace();
    	 }
   }
}

Output:

2014-02-15 10:22:12 PM

Related Posts:

1. Java – SimpleDateFormat examples
2. Java – Convert String to 24 hour date format
3. Java – Convert Date to String
4. Java – Convert String to Date
5. Java 8 – Calculate Days between two dates