Calender in java returning the same date when changing the time zone?

I am working on a project where I have to manipulate the dates. Here is the code snipper I have My time zone is IST and the conversion time zone is CST.

public class Sample {
public static Long time = 1418187600l;
public static TimeZone tz1 = TimeZone.getTimeZone("US/Central");


public static void main(String[] args) {
    Calendar c1 = Calendar.getInstance();
    System.out.println(c1.getTime()); // output1 
    c1.setTimeInMillis(time*1000);
    System.out.println(c1.getTime());//output 2
    System.out.println(c1.get(Calendar.DATE));
    c1.setTimeZone(tz1);;
    System.out.println(c1.getTime()); //output 3
    System.out.println(c1.get(Calendar.DATE));
}

}

When I ran the program, I got 

Wed Dec 10 13:03:42 IST 2014

for line which was correct.

Then set the time to 1418187600, this output was also correct.

Wed Dec 10 10:30:00 IST 2014

However when the set the timezone to CST, and tried outputting the date, it returned the same

Wed Dec 10 10:30:00 IST 2014

while it should have returned Dec 09 2014 23:00:00.

However when I tried Calendar.data, it showed the correct date. can anyone explain to me why this is the case?

Jon Skeet
people
quotationmark

You're printing out a java.util.Date (the result of calling getTime()). A Date doesn't include time zone information at all - Date.toString() always displays the point in time represented by that Date in the default time zone.

Basically, you should avoid calling Date.toString() - it's the cause of much confusion. Use a SimpleDateFormat instead, which you can set to use a particular time zone.

Alternatively, use the java.time classes if you're using Java 8, or Joda Time otherwise - both are much better options than java.util.Date and java.util.Calendar.

people

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