I've got this weird issue. The following piece of code outputs my local time instead of the time of the set timezone.
What am I doing wrong? How could I get a calendar object (or a Date) with values set to the preferred timezone?
Kurt Van Etten
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Joined: Sep 07, 2010
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Hi,
The time is set correctly in your Calendar instance; it's just that when you output the time value, it is displayed according to the local time zone (e.g., your time zone).
To display the time according to the time zone you've set for the Calendar, you could use a DateFormat object and do something like the following:
(Although for this particular example there is no real reason to create a Calendar object with the particular time zone; the DateFormat is doing all the work so I could just have it display the local time.)
Dm Laf
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Joined: Mar 23, 2004
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Hi Kurt,
First of all, I'd like to thank you for your immediate response.
Now..What I do not understand is that if the getTime() method always displays my local time, disregarding the timezone parameter in the getInstance(Timezone tz) method, then whats the point of supplying one? Is it a bug?
I dont just need to output the date..I need a calendar object because I am working on a client/server application and several components on my client need to contain the server time. These components are setting their values based on the Calendar.getTime() method. So you see where my issue is..?
You're not printing a Calendar, you're printing a Date. And Date is an encapsulation of a point in time, represented internally by a long value equal to the number of milliseconds since a certain instant of time known as the Epoch.
Now Date doesn't have a TimeZone. Date.toString(), which is what is called when you System.out.println a Date, uses a TimeZone to produce a human-readable form of the encapsulated long value. That TimeZone is your default, or local TimeZone.
You've already been given good advice about how to produce the output you want. I just thought you should also understand a little more about the often-misunderstood java.util.Date. To repeat: Date doesn't have a TimeZone. It represents a point in time, which is the same instant everywhere, whether it's dawn in New York or dusk in New Delhi.
luck, db
There are no new questions, but there may be new answers.
Dm Laf
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Joined: Mar 23, 2004
Posts: 10
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Thank you guys for your responses.
I think I may have been misunderstood in my original post and that is probably why every1 is giving me examples on how to output the date in different timezones.
That is NOT why I am looking an answer for. All I need to know is why Calendar.getInstance(Timezone ).getTime() ALWAYS displays my local time. I would have expected that since I am supplying a timezone, the getTime() method of the Calendar class, outputs the time for that zone.
Like I said on my second post, I have a client/server application and I need to find a way to populate fields on the client with the server calendar details. These fields (and I am not talking about plain labels or texts), accept only Calendar objects.
Thank you again for your time
PS: Darryl: " It represents a point in time, which is the same instant everywhere, whether it's dawn in New York or dusk in New Delhi." I agree. But the same instance of time in New Delhi it could be 08.00am and in Adelaide, Australia it could be 11.00am. Again, since I am supplying a timezone in the Calendar, I'd expect it would return the corresponding time.
Mike Simmons
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Dim Stef wrote:All I need to know is why Calendar.getInstance(Timezone ).getTime() ALWAYS displays my local time.
Because Calendar.getTime() returns a Date, and you are calling the toString() method on java.util.Date. Go and read the documentation for this method. The toString() method on Date uses your local time, period. That's why you're seeing local time.
Dim Stef wrote:I would have expected that since I am supplying a timezone, the getTime() method of the Calendar class, outputs the time for that zone.
You are supplying a timezone to the Calendar, but then you are getting a Date. As Darryl correctly said in his post, a Date has no timezone of its own. Instead, the toString() method does always use local time, period.
Dim Stef wrote:Like I said on my second post, I have a client/server application and I need to find a way to populate fields on the client with the server calendar details. These fields (and I am not talking about plain labels or texts), accept only Calendar objects.
Well, you can go ahead and do that. The problem right now though is that you're trying to print the time associated with a Calendar, and you're doing it in a way that loses the time zone information. The Calendar itself may be perfectly representing what you want, but Date's toString() is giving you local time, period.
Solution: don't use Date's toString(). Ignore it. If you want to know what's in the Calendar, use the Calendar's own toString() method (which gives ugly but detailed output). Or use getTimeZone() to get the time zone, and other get() methods to get other info. And if you want to print a Date object in a particular time zone, use DateFormat as discussed above. Calling Date's toString() will never, ever do what you want here, no matter how much you think it should be otherwise.
Dm Laf
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Joined: Mar 23, 2004
Posts: 10
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Thank you Mike for taking the time to answer to my question.
I totally agree with you that Date does not have a timezone, but the way I see it, if I live in Russia and I am asking Java to give me the current date in India then Calendar.getInstance(Timezone of India).getTime() should return the current time in India. Returning the local time is fundamentally incorrect. Period.
Playing with toString() methods just to get (and not output..) a time in a different timezone is just not right.
I may have to report to Oracle as an issue that require further attention.
Dim Stef wrote:Thank you Mike for taking the time to answer to my question.
I add my thanks for expressing many of the things I said in a way more suited to the OP's understanding (no sarcasm intended)
Dim Stef wrote:I totally agree with you that Date does not have a timezone, but the way I see it, if I live in Russia and I am asking Java to give me the current date in India then Calendar.getInstance(Timezone of India).getTime() should return the current time in India.
Unfortunate for you that the way you see it isn't the way it was designed to work.
Dim Stef wrote:Returning the local time is fundamentally incorrect. Period.
You still don't get it, do you? A point in time is the same instant all over the world, all over the universe. The only thing that's incorrect here is your flawed understanding and expectations.
Dim Stef wrote:Playing with toString() methods just to get (and not output..) a time in a different timezone is just not right.
Nobody suggested playing with toString methods. The suggestions were to use the SimpleDateFormat class, which is the correct approach.
Again, a Date encapsulates a point, or an instant, in time. When it's noon in London it's 17:30 in Delhi. That instant is the same point in time. Only the representation of that instant in time changes with the timezone, not the instant itself.
Dim Stef wrote:I may have to report to Oracle as an issue that require further attention.
Sorry but
Dim Stef wrote:Thank you very much for all your responses guys.
Youre welcome? but if you fail to understand the concepts presented here, you're going to face a lot of grief down the line.
Dim Stef wrote:I totally agree with you that Date does not have a timezone, but the way I see it, if I live in Russia and I am asking Java to give me the current date in India then Calendar.getInstance(Timezone of India).getTime() should return the current time in India. Returning the local time is fundamentally incorrect. Period.
I'm not sure why we're not getting through to you on this one. You're *NOT* asking Java to give you the Date in India. You're asking Java to give you the Date of a Calendar with a TZ of India, but you're still confused as to what a Date is.
Dates are UTC. Look at the Date docs. See anything about timezones? No. Think of a Date as an absolute timestamp reference, to which timezones may be applied. No matter what TZ you give a *Calendar*, the *underlying absolute moment in time* is precisely the same.
I may have to report to Oracle as an issue that require further attention.
David Newton wrote:I'm not sure why we're not getting through to you on this one. You're *NOT* asking Java to give you the Date in India. You're asking Java to give you the Date of a Calendar with a TZ of India, but you're still confused as to what a Date is.
"You're *NOT* asking Java to give you the Date in India. You're asking Java to give you the Date of a Calendar with a TZ of India"... Do you hear yourself what you just said?
Please stop repeating that Date has no timestamp. I think we have established that already. I am not arguing that! What I am arguing is the following piece of code
It may be the same *underlying absolute moment in time* BUT 2010/12/05 04:00PM is not the same as 2010/12/04 :00AM nor 2010/12/04 03:AM. That is my argument here. That is the reason I am asking Calendar for the DETAILS of the *underlying absolute moment in time* in different TIMEZONES! Calendar is sending me a Date object, but I expect it to be modified according to the timezone. Otherwise, what is the point of supplying a timezone to the Calendar obj?
Dm Laf wrote:Calendar is sending me a Date object, but I expect it to be modified according to the timezone.
Then you expect incorrectly. That has already been explained in this thread so I won't explain it again. I will just say that trying to program based on what you expect to happen, instead of based on what actually does happen, is not going to get you anywhere. In fact it's just a waste of time.
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