SimpleDateFormatter returns two different time zones

Question

I have these two strings as input strings

03/12/16
03/14/16

I make a single SimpleDateFormatter object to get the date difference like this

DateFormat formatter = new SimpleDateFormat("MM/dd/yy",Locale.US);
Date dateChkIn = formatter.parse("03/12/16");
System.out.println("Checkin date at nights check - "+dateChkIn.toString());
Date dateChkOut = formatter.parse("03/14/16");
System.out.println("Checkout date at nights check - "+dateChkOut.toString());
Long numberOfNghtsCalc = ((dateChkOut.getTime() - dateChkIn.getTime()) / 86400000L);
System.out.println("number of nigts calculated - "+ numberOfNghtsCalc);

Below is my output in the server

Checkin date at nights check - Sat Mar 12 00:00:00 EST 2016
Checkout date at nights check - Mon Mar 14 00:00:00 EDT 2016
number of nigts calculated - 1

Expected output is number of nigts calculated - 2 Please note the two different Time Zones which returned from the formatter

Update : 13-Mar-2016 is considered as DST changing date. Therefore my calculation is getting wrong. (divide by 86400000L)

Start by using either Java 8's Time API or JodaTime to calculate the difference between dates ... did you happen to cross over a daylight savings boundary? — MadProgrammer, Sep 25 '15 at 06:58
@MadProgrammer I appreciate your comment. But my system is using Java 1.5 . This code is in my production environment. All these time; it worked perfectly. Suddenly this was occured. — Jude Niroshan, Sep 25 '15 at 07:00
Well, Joda-Time supports Java 5, but you could even use `Calendar` — MadProgrammer, Sep 25 '15 at 07:01
try add `formatter.setTimeZone(TimeZone.getTimeZone("GMT"));` below the `SimpleDateFormat` — cw fei, Sep 25 '15 at 07:30
@cwfei It might not work. All servers are set to US time zone. EDT. I want to do all calculations upon that. — Jude Niroshan, Sep 25 '15 at 07:32
you may read this http://stackoverflow.com/questions/2532729/daylight-saving-time-and-time-zone-best-practices — cw fei, Sep 25 '15 at 08:06

Jude Niroshan · Accepted Answer · 2015-10-02T04:42:31.420

I found the solution. I got to know that best solution would be use Joda Time. But with least change in the existing code, I think this tricky way will be better. Please edit this answer if you see any drawbacks.

    List<Date> dates = new ArrayList<Date>();
    Calendar calendar = new GregorianCalendar();
    calendar.setTime(dateChkIn);

    Date result = null;
    while (calendar.getTime().before(dateChkOut)){
            result = calendar.getTime();


            dates.add(result);
            calendar.add(Calendar.DATE, 1);
    }
    System.out.println("DAYS CALCULATED BY NEW SOLUTION: " + dates.size());
    newNumberOfNghtsCalc = (long) dates.size();
    dates.clear();

This has actually reduced the running time!

Time taken for code in Question : 275000 (in nano seconds)

Time taken for New solution: 103000

score 1 · Answer 2 · answered Sep 25 '15 at 07:01

1

on next 13 March 2016 change hour by EST to EDT. So SimpleDateFormat takes care of this change.

Go here

answered Sep 25 '15 at 07:01

Joe Taras

15,166
7
42
55

I am sorry. I don't know much about **Daylight saving time**. This issue was reported in our production. Should I need to do any code level changes to handle this? Is this a very rare occation? How should I inform this to my US client? – Jude Niroshan Sep 25 '15 at 07:11
@JudeNiroshan: Not rare! Every year you have the same issue when change EST -> EDT and viceversa. The same issue you have if you work with different time zone (i.e. Europe vs America). – Joe Taras Sep 25 '15 at 07:29
But my question is why **SimpleDateFomatter** returned two different timezones ? EST for 12th and EDT for 16th ? – Jude Niroshan Sep 25 '15 at 07:31
@Jude: SimpleDateFormatter returns the same time zone, but time zone change in that area. So SDF is sensible to this change. – Joe Taras Sep 25 '15 at 07:40

score 1 · Answer 3 · answered Sep 25 '15 at 07:02

1

The difference is of caused by the Daylight Saving Time, which for 2016 is scheduled as March 13, 2016. Here you can read a short article on the difference between EDT and EST.

answered Sep 25 '15 at 07:02

Gergely Bacso

14,243
2
44
64

Arvind Kumar Avinash · Answer 4 · 2021-05-02T19:13:08.103

java.time

I recommend you use the modern, java.time date-time API.

Demo:

import java.time.Duration;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.time.temporal.ChronoUnit;
import java.util.Locale;

public class Main {
    public static void main(String[] args) {
        DateTimeFormatter dtf = DateTimeFormatter.ofPattern("M/d/uu", Locale.ENGLISH);
        LocalDate dateChkIn = LocalDate.parse("03/12/16", dtf);
        LocalDate dateChkOut = LocalDate.parse("03/14/16", dtf);
        long days = ChronoUnit.DAYS.between(dateChkIn, dateChkOut);
        System.out.println(days);
    }
}

Output:

Learn about the modern date-time API from Trail: Date Time.

For any reason, if you have to stick to Java 6 or Java 7, you can use ThreeTen-Backport which backports most of the java.time functionality to Java 6 & 7.
If you are working for an Android project and your Android API level is still not compliant with Java-8, check Java 8+ APIs available through desugaring and How to use ThreeTenABP in Android Project.

SimpleDateFormatter returns two different time zones

4 Answers4

java.time