TimeZone Conversion

[sushil java]

Please help to convert one timeZone to another.Given method is converting the given time to server Timezone where the server is located.But it is not converting from server time to any other user time.

public static Calendar getTimeZoneDate(Date userDate,String userTimeZone,String serverTimeZone){
 Calendar serverCalendar=null;
 Calendar localCalendar=new GregorianCalendar(TimeZone.getTimeZone(userTimeZone),Locale.US);
 int DATE=userDate.getDay();
 int MONTH=userDate.getMonth();
 int YEAR=1900+userDate.getYear();
 
 int HOUR_OF_DAY=userDate.getHours();
 int MINUTE=userDate.getMinutes();
 //int SECOND=userDate.getMinutes();
 //localCalendar.set(YEAR,MONTH,DATE,HOUR_OF_DAY,MINUTE,SECOND);
 localCalendar.set(Calendar.DATE, DATE);
 localCalendar.set(Calendar.MONTH, MONTH);
 localCalendar.set(Calendar.YEAR, YEAR);    
 localCalendar.set(Calendar.HOUR_OF_DAY, HOUR_OF_DAY);               // 0..23
 localCalendar.set(Calendar.MINUTE, MINUTE);
 //localCalendar.set(Calendar.SECOND, SECOND);
 
 BVLog.error("I'n in TimeZoneUtil-->"+localCalendar.getTime().toString());
 if(serverTimeZone !=null){
 serverCalendar=new GregorianCalendar(TimeZone.getTimeZone(serverTimeZone),Locale.ENGLISH);
 }
 else{
 BVLog.error("I'n in TimeZoneUtil Else Part");
 serverCalendar=new GregorianCalendar();  
 }
 serverCalendar.setTimeInMillis(localCalendar.getTimeInMillis());
 BVLog.error("I'n in TimeZoneUtil serverCalendar -->"+serverCalendar.getTime().toString());
 return serverCalendar;
}
 

[Jesper de Jong]

Working with dates, times and timezones in Java can be confusing.

One thing that you need to be aware of is that class java.util.Date does not store information about timezones. A java.util.Date is a kind of fancy wrapper that stores a number of milliseconds since January 1, 1970, 00:00:00 GMT. So in a way you can regard a java.util.Date as always being in the GMT timezone.

A Calendar does have a TimeZone property, but setting or modifying it does not convert the date and time that the calendar holds to a different timezone.

When you convert a Date to a String by using a DateFormat object, then you can set the timezone on the DateFormat object, and it will convert your Date to a String that represents the date and time in that timezone. Likewise when you have a String that contains a Date and you use a DateFormat object to parse it. For example:

// Suppose this is a date and time in the EST timezone
String value = "2006-11-28 09:45:12";
 
DateFormat df1 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
df1.setTimeZone(TimeZone.getTimeZone("EST"));
 
// Parses the value and assumes it represents a date and time in the EST timezone
Date d = df1.parse(value);
 
DateFormat df2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
df2.setTimeZone(TimeZone.getTimeZone("CET"));
 
// Formats the date in the CET timezone
System.out.println(df2.format(d));

This prints out:

2006-11-28 15:45:12

[Jeremy James Brown]

"A Calendar does have a TimeZone property, but setting or modifying it does not convert the date and time that the calendar holds to a different timezone."

Genius, pure genius!