Difference Between Java Hh:Mm and Hh:Mm on Simpledateformat

Difference between hh:mm a and HH:mm a

Updated Answer

Here the problem is with Program flow

SimpleDateFormat formatter = new SimpleDateFormat("dd MMM yyyy HH:mm a");

this simple date formatter is used to format the date string the Date object is created, here is the important part of answer

As you are using HH instead of hh, the SimpleDateFormater considers that provided date string is in 24-Hour Format and simply ignores the AM/PM marker here.

The Date Object from constructed from this SimpleDateFormatter is passed to the

DateFormat df = new SimpleDateFormat("dd MMM yyyy HH:mm a", locale);

That's why it's printing

newDate = 23 Dec 2015 01:04 AM

if you change the line

SimpleDateFormat formatter = new SimpleDateFormat("dd MMM yyyy HH:mm a");

with

SimpleDateFormat formatter = new SimpleDateFormat("dd MMM yyyy hh:mm a");

Everything will go smooth as it should!

Note : when creating a locale you should pass the language code to the Locale() constructor. en-us not en_us.

IMP : Code is tested on Java 8 also. Java(TM) SE Runtime Environment (build 1.8.0_121-b13)

calculate time difference between two hours in timeformat hh:mm:ss java

The answer by Michael is good (+1). Allow me to add that you don’t need to mention any formatter (though I also see the advantage of being explicit about the format) and you don’t need to invent an artificial and probably incorrect date to deal with the 24:00 issue.

        LocalTime start = LocalTime.parse(timeStart);
        LocalTime stop = LocalTime.parse(timeStop);
        if (stop.isAfter(start)) { // the normal situation
            System.out.println(formatDuration(Duration.between(start, stop)));
        } else if (stop.equals(LocalTime.MIDNIGHT)) {
            System.out.println(
                    formatDuration(Duration.between(start, stop).plusDays(1)));
        } else {
            System.out.println("End time " + timeStop + " was before start time " + timeStart);
        }

I am assuming that the times are on the same date except that an end time of 00:00:00 would mean midnight at the end of the day (sometimes called 24.00 where I come from). If you need to calculate, say from 13:00 one day to 13:00 to the next day as 24 hours, just delete the second if condition and the last else block.

Feeding your example input gives the output you asked for:

04:57:15
01:00:00
12:05:00
11:55:00

As Michael mentions, the toMinutesPart and toSecondsPart methods were introduced in Java 9. For how to format the duration in earlier Java versions see my answer here.

What went wrong in your code?

To parse times on a 24 hour clock correctly (12:05:00, 13:00:00, 14:00:00, 15:00:58) you need to use uppercase HH for hour of day. Lowercase hh is for hour within AM or PM from 01 to 12 inclusive. When you don’t specify AM or PM, AM is used as default. So 10:03:43 is parsed as you expected. Funnily 15:00:58 is too even though there is no 15:00:58 AM. SimpleDateFormat just extrapolates. The trouble comes with 12:05:00 since 12:05:00 AM means 00:05:00. On my computer I got 23:55:00 (not 00:05:00, as you said you got). This is because you had first altered the start time into 24:00:00 and next calculated the time from 00:05:00 to 24:00:00, which is 23:55:00. Since you know which time is the start time and which is the end time, you probably shouldn’t swap them in the case where they seem to be in the wrong order. In your last example I got 23:55:00 too. What happens is the same except the times aren’t swapped since 00:05:00 is already before 24:00:00.

Difference between two times stored as Strings

You can do it using SimpleDateFormat and Date:

import java.text.ParseException; 
import java.text.SimpleDateFormat; 
import java.util.Date; 

public static long date_hour_diff(String start_date, String end_date) { 
  SimpleDateFormat simple_date_format = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss"); 
  try {  
    Date parsed_start_date = simple_date_format.parse(start_date); 
    Date parsed_end_date = simple_date_format.parse(end_date); 
  
    long time_diff = d2.getTime() - d1.getTime(); 
    long diff_hours = (time_diff / (1000 * 60 * 60)) % 24; 
    return diff_hours;
  } catch (ParseException e) { 
      Log.e(TAG, "Date is not valid.");
  } 
}

Need to get the time difference between the two dates in hh:mm format

My solution:

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class TimeDiff {

    public static void main(String[] args) throws ParseException {

        // Setup
        SimpleDateFormat dateFormat = new SimpleDateFormat(
                "MM/dd/yyyy HH:mm:ss");
        long second = 1000l;
        long minute = 60l * second;
        long hour = 60l * minute;

        // parsing input
        Date date1 = dateFormat.parse("02/26/2014 09:00:00");
        Date date2 = dateFormat.parse("02/26/2014 19:30:00");

        // calculation
        long diff = date2.getTime() - date1.getTime();

        // printing output
        System.out.print(String.format("%02d", diff / hour));
        System.out.print(":");
        System.out.print(String.format("%02d", (diff % hour) / minute));
        System.out.print(":");
        System.out.print(String.format("%02d", (diff % minute) / second));
    }

}

Keep in mind, that dates are not as easy as you could expect. There are leap seconds and all kind of weird stuff.

Difference between kk and HH in date formatting java

The two formats essentially do the same thing but differ in how they handle midnight. kk will format midnight to 24:00 whereas HH will format to 00:00. The hours in a day in k are 1-24 and in H are 0-23

It's always worth checking the java documentation as it generally provides very useful explanations as well as examples of uses.

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