Puzzling Parsing of Dates

[raja patil]

hello

I am new to Java and developing First Java Application. Please refer following code and the output.

System is Kubuntu 9.10 JDK 1.6 Repository Install, STS 2.3.2.

public static void main(String[] args) {

// Mon Jan 01 05:53:20 IST 1900
SimpleDateFormat fmt = new SimpleDateFormat("EEE MMM dd HH:mm:ss zzz yyyy");
TimeZone tz = TimeZone.getDefault();

System.out.println("RawOffset = " + tz.getRawOffset() + " useDaylightTime = " + tz.useDaylightTime());
try {
Date dt1 = fmt.parse("Mon Jan 01 05:30:00 IST 1900");
Date dt2 = fmt.parse("Mon Jan 01 05:29:59 IST 1900");

System.out.println("date = " + dt1 + " offset = " + tz.getOffset(dt1.getTime()) + " getTime = "
+ dt1.getTime());
System.out.println("date = " + dt2 + " offset = " + tz.getOffset(dt2.getTime()) + " getTime = "
+ dt2.getTime());
}
catch (ParseException e) {
e.printStackTrace();
}
}
}

RawOffset = 19800000 useDaylightTime = false
date = Mon Jan 01 05:53:20 IST 1900 offset = 21200000 getTime = -2208988800000
date = Mon Jan 01 05:29:59 IST 1900 offset = 19800000 getTime = -2208988801000

I am confused why diff of 1 sec at threshold of timezone offset of 05:30 is converting date to 05:53:20 when
the raw date millis have changed correctly by 1 sec. You can see that offset has also shifted by 23:20 so
addition of 23:20 can be understood but why should it happen ? How can I get correct time of 05:30 if its
default behavior.

Thanks and Best Regards.

Raja

[Michael Angstadt]

Hi raja, welcome to JavaRanch! Please UseCodeTags, as it makes your code easier to read and fix.

It seems like it's not parsing your first Date correctly. What happens when you manually pull the minute value out of the Date?

Calendar c = Calendar.getInstance();
c.setTime(dt1);
System.out.println(c.get(Calendar.MINUTE));

[raja patil]

Thanks Michael Angstadt,

Here is Out put

RawOffset = 19800000 useDaylightTime = false
date = Mon Jan 01 05:53:20 IST 1900 offset = 21200000 getTime = -2208988800000
date = Mon Jan 01 05:29:59 IST 1900 offset = 19800000 getTime = -2208988801000
dt1.Calendar.MINUTE = 53

regards

Raja

[sai prashanth]

I tried to run your code and this is my output. I dont see anything wierd here:

RawOffset = 19800000 useDaylightTime = false
date = Sun Dec 31 21:30:00 CST 1899 offset = 21200000 getTime = -2208976200000
date = Sun Dec 31 21:29:59 CST 1899 offset = 21200000 getTime = -2208976201000

[raja patil]

sai prashanth wrote:I tried to run your code and this is my output. I dont see anything wierd here:

RawOffset = 19800000 useDaylightTime = false
date = Sun Dec 31 21:30:00 CST 1899 offset = 21200000 getTime = -2208976200000
date = Sun Dec 31 21:29:59 CST 1899 offset = 21200000 getTime = -2208976201000

Thanks Sai prashanth have you tried with IST (india not Irish i.e. GMT+0530) rather than CST timezone ?
Please noticed offset values 19800000 and 21200000 that is causing problem I believe.
another thing is that from 05:29:59 to 05:30:00 there is jump of 00:23:20 and after that
it increments linearly with input value.

Thanks and regards

Raja

[raja patil]

hello,

I just found this http://72.5.124.102/thread.jspa?messageID=10811150 which explains things about IST timezone
is really java gets confused with 3 letter timezone ? If yes then what shout I use so that java wont get confused.

Thanks and regards

Raja

[David Newton]

http://java.sun.com/j2se/1.5.0/docs/api/java/util/TimeZone.html

See specifically the section on three-letter timezone names.

[raja patil]

Thanks to all who contributed to this thread,

It Seems that there is No problem with IST. The history of IST (Indian Standard Time) Like that only.
Before 1900 there was no definition of IST.
initially IST was using Madras (Chennai) Time then Kolkata time then after Independence in 1947
its using Ujain i.e. Meridian Passing through almost centre of the state so there are three different
offsets the listing below clearly indicates that. During analysis of this issue I learnt that timezones
are fixed by Politicians and not by scientists thats why there are many such issues to be dealt with
by programmers by simply setting time zone to GMT+0530 all the date time issues get vanished.

 
public class Test4Dates {

	/**
	 * @param args
	 */
	public static void main(String[] args) {

		// Mon Jan 01 05:53:20 IST 1900
		SimpleDateFormat	fmt		= new SimpleDateFormat("EEE MMM dd HH:mm:ss Z yyyy");

		TimeZone			old_tz	= TimeZone.getDefault();

		System.out.println("Default tz Name = " + TimeZone.getDefault().getID());

//      TimeZone.setDefault(TimeZone.getTimeZone("GMT+0530"));
//      System.out.println("Default tz Name = " + TimeZone.getDefault().getID());

		Calendar	c	= Calendar.getInstance();
		TimeZone	tz	= TimeZone.getDefault();

		System.out.println("tz Name = " + tz.getID() + " RawOffset = " + tz.getRawOffset() + " useDaylightTime = "
						   + tz.useDaylightTime() + "\n");
		for (int i = 1900; i < 1950; i = i + 1) {
			try {

				Date	dt1	= fmt.parse("Mon Jan 01 05:30:00 IST " + i);

				c.setTime(dt1);
				System.out.println("date = " + dt1 + " offset = " + tz.getOffset(dt1.getTime()) + " getTime = "
								   + dt1.getTime() + " mins = " + c.get(Calendar.MINUTE));

				Date	dt2	= fmt.parse("Mon Jan 01 05:29:59 IST " + i);

				c.setTime(dt2);
				System.out.println("date = " + dt2 + " offset = " + tz.getOffset(dt2.getTime()) + " getTime = "
								   + dt2.getTime() + " mins = " + c.get(Calendar.MINUTE) + "\n");

				}
			catch (ParseException e) {
				e.printStackTrace();
				}
			}
		System.out.println("Default tz Name = " + TimeZone.getDefault().getID());
		TimeZone.setDefault(old_tz);
		System.out.println("Default tz Name = " + TimeZone.getDefault().getID());
		}
	}

Default tz Name = Asia/Kolkata
tz Name = Asia/Kolkata RawOffset = 19800000 useDaylightTime = false

date = Mon Jan 01 05:53:20 IST 1900 offset = 21200000 getTime = -2208988800000 mins = 53
date = Mon Jan 01 05:29:59 IST 1900 offset = 19800000 getTime = -2208988801000 mins = 29

date = Tue Jan 01 05:53:20 IST 1901 offset = 21200000 getTime = -2177452800000 mins = 53
date = Tue Jan 01 05:53:19 IST 1901 offset = 21200000 getTime = -2177452801000 mins = 53

date = Wed Jan 01 05:53:20 IST 1941 offset = 21200000 getTime = -915148800000 mins = 53
date = Wed Jan 01 05:53:19 IST 1941 offset = 21200000 getTime = -915148801000 mins = 53

date = Thu Jan 01 06:30:00 IST 1942 offset = 23400000 getTime = -883612800000 mins = 30
date = Thu Jan 01 06:29:59 IST 1942 offset = 23400000 getTime = -883612801000 mins = 29

date = Fri Jan 01 06:30:00 IDT 1943 offset = 23400000 getTime = -852076800000 mins = 30
date = Fri Jan 01 06:29:59 IDT 1943 offset = 23400000 getTime = -852076801000 mins = 29

date = Sat Jan 01 06:30:00 IDT 1944 offset = 23400000 getTime = -820540800000 mins = 30
date = Sat Jan 01 06:29:59 IDT 1944 offset = 23400000 getTime = -820540801000 mins = 29

date = Mon Jan 01 06:30:00 IDT 1945 offset = 23400000 getTime = -788918400000 mins = 30
date = Mon Jan 01 06:29:59 IDT 1945 offset = 23400000 getTime = -788918401000 mins = 29

date = Tue Jan 01 05:30:00 IST 1946 offset = 19800000 getTime = -757382400000 mins = 30
date = Tue Jan 01 05:29:59 IST 1946 offset = 19800000 getTime = -757382401000 mins = 29

Default tz Name = Asia/Kolkata
Default tz Name = Asia/Kolkata

with TimeZone "GMT+0530"

Default tz Name = Asia/Kolkata
Default tz Name = GMT+05:30
tz Name = GMT+05:30 RawOffset = 19800000 useDaylightTime = false

date = Mon Jan 01 05:30:00 GMT+05:30 1900 offset = 19800000 getTime = -2208988800000 mins = 30
date = Mon Jan 01 05:29:59 GMT+05:30 1900 offset = 19800000 getTime = -2208988801000 mins = 29

date = Tue Jan 01 05:30:00 GMT+05:30 1901 offset = 19800000 getTime = -2177452800000 mins = 30
date = Tue Jan 01 05:29:59 GMT+05:30 1901 offset = 19800000 getTime = -2177452801000 mins = 29

[b]All in between same[/b]

date = Sat Jan 01 05:30:00 GMT+05:30 1949 offset = 19800000 getTime = -662688000000 mins = 30
date = Sat Jan 01 05:29:59 GMT+05:30 1949 offset = 19800000 getTime = -662688001000 mins = 29

Default tz Name = GMT+05:30
Default tz Name = Asia/Kolkata

Thanks and best regards

Raja