Have tried out a couple of code snippets to handle timezone corrections in Java code that’ll take into account Daylight Savings Time (DST) settings. None of them really suited our need; so I had to modify a particular code snippet which I found to be closer to what I was expecting.
Here’s the modified code:.
private static Date offsetTimeZone(Date date, String fromTZ, String toTZ){
// Construct FROM and TO TimeZone instances
TimeZone fromTimeZone = TimeZone.getTimeZone(fromTZ);
TimeZone toTimeZone = TimeZone.getTimeZone(toTZ);
// Get a Calendar instance using the default time zone and locale.
Calendar calendar = Calendar.getInstance();
// Set the calendar's time with the given date
calendar.setTimeZone(fromTimeZone);
calendar.setTime(date);
System.out.println("Input: " + calendar.getTime() + " in " + fromTimeZone.getDisplayName());
// FROM TimeZone to UTC
calendar.add(Calendar.MILLISECOND, fromTimeZone.getRawOffset() * -1);
if (fromTimeZone.inDaylightTime(calendar.getTime())) {
calendar.add(Calendar.MILLISECOND, calendar.getTimeZone().getDSTSavings() * -1);
}
// UTC to TO TimeZone
calendar.add(Calendar.MILLISECOND, toTimeZone.getRawOffset());
if (toTimeZone.inDaylightTime(calendar.getTime())) {
calendar.add(Calendar.MILLISECOND, toTimeZone.getDSTSavings());
}
return calendar.getTime();
}
Sample Method Invocation: offsetTimeZone(new Date(), “Asia/Kolkata”, “US/Central”)
One good thing about this solution is that it’ll take care of DST settings in both the timezones (FROM and TO).
Singaram Subramanian
singztechmusings.wordpress.com 
This is useful but seems somewhere it went wrong.
the above code gives wrong output in the below scenario : Could you please help in update this?
import java.util.Calendar;
import java.util.TimeZone;
public class Test {
public static void main(String[] args) throws Exception {
// Construct FROM and TO TimeZone instances
TimeZone fromTimeZone = TimeZone.getTimeZone(“America/Chicago”);
TimeZone toTimeZone = TimeZone.getDefault();
// Get a Calendar instance using the default time zone and locale.
Calendar calendar = Calendar.getInstance();
// Set the calendar’s time with the given date
calendar.setTimeZone(fromTimeZone);
// calendar.setTime(new Date());
calendar.set(2011, 4 – 1, 12 – 1); // APR 12 2011
calendar.set(Calendar.HOUR, 12 – 1); // 11
calendar.set(Calendar.MINUTE, 00);
calendar.set(Calendar.SECOND, 00);
calendar.set(Calendar.AM_PM, Calendar.PM);
System.out.println(“Input : ” + calendar.getTime() + ” in ”
+ fromTimeZone.getDisplayName());
// FROM TimeZone to UTC
int rawOffset_from_UTC = fromTimeZone.getRawOffset();
calendar.add(Calendar.MILLISECOND, rawOffset_from_UTC * -1);
//System.out.println(rawOffset_from_UTC);
if (fromTimeZone.inDaylightTime(calendar.getTime())) {
int dstOffset_from_UTC = calendar.getTimeZone().getDSTSavings();
//System.out.println(dstOffset_from_UTC);
calendar.add(Calendar.MILLISECOND, dstOffset_from_UTC * -1);
}
// UTC to TO TimeZone
calendar.add(Calendar.MILLISECOND, toTimeZone.getRawOffset());
if (toTimeZone.inDaylightTime(calendar.getTime())) {
calendar.add(Calendar.MILLISECOND, toTimeZone.getDSTSavings());
}
System.out.println(“Output: ” + calendar.getTime() + ” in ”
+ toTimeZone.getDisplayName());
}
}
————————————————————–
Actual Output :
————————————————————–
Input : Tue Apr 12 00:00:00 EDT 2011 in Central Standard Time
Output: Tue Apr 12 01:00:00 EDT 2011 in Eastern Standard Time
————————————————————–
Expected output :
————————————————————–
Input : Tue Apr 12 00:00:00 EDT 2011 in Central Standard Time
Output: Tue Apr 13 01:00:00 EDT 2011 in Eastern Standard Time
Differed at the out put date 13.
Sorry about that. Its correct. I misunderstood and my brain is locked.
that’s fine, it happens!! 🙂
[…] It’s over the web. Could have googled. Anyways, here is a version for you (shamelessly picked and modified from here): […]
Thank you! This saved me a ton of time!
I was thinking about moving my entire work from Java Date (which sucks) to Joda DateTime and wouldve done so, if I hadn’t found this post.