Java set timezone at runtime

I am working on a desktop application. It would get input as a text file from user having contents like this :

..................................   
..................................

Mon Jul  9 14:41:07 MDT 2012
..................................
..................................
..................................

I am using this information and creating a timeseries chart using jfreechart library. Timezone could be anything available in the world. But when I use this file its default timezone is sytem's timezone(IST) so doesn't show MDT time. When I tried to capture timezone from date and then used

TimeZone.setDefault(TimeZone.getTimeZone("MDT"));

It didn't work. How can I change the default timezone in Java when I am having abbreviation for timezone like MDT, CDT etc?

MDT is not the timezone key, it is the short display name of the timezone, so TimeZone.getTimeZone("MDT") would return default time zone which is GMT. The keys for Mountain Time are MST,MST7MDT etc. So, you need to identify the key of the timezone. Please note there are many different keys for the same short display name e.g. for MDT shortName there are keys with US/Mountain, US/Arizona, SystemV/MST7MDT, Navajo, Mexico/BajaSur, MST7MDT and MST.

Theres no timezone called MDT, it is MST7MDT. Use:

TimeZone.setDefault(TimeZone.getTimeZone("MST7MDT"));

Also see Java's java.util.TimeZone

Use the setTimeZone(...) method from the Calendar class.

dirtyhandsphp

Thanks Guys. Thanks for quick responses. @vikas your response proves to be more useful. I am using following code and it worked well.

String timezoneLongName = "";

String fileTimeZone     = "MDT"; //timezone could be anything, getting from file.

Date date            = new Date();
String TimeZoneIds[] = TimeZone.getAvailableIDs();

for (int i = 0; i < TimeZoneIds.length; i++) {

    TimeZone tz   = TimeZone.getTimeZone(TimeZoneIds[i]);
    String tzName = tz.getDisplayName(tz.inDaylightTime(date),TimeZone.SHORT);

    if(fileTimeZone.equals(tzName)){
        timezoneLongName = TimeZoneIds[i];
        break;
    }
}

if(timezoneLongName != null && !timezoneLongName.isEmpty() && !timezoneLongName.trim().isEmpty() && timezoneLongName.length() != 0){
    TimeZone.setDefault(TimeZone.getTimeZone(timezoneLongName));
}

Although there are more than one entries for "MDT" timezone but it resolves my problem without any problem at first match itself. I have tested code on CDT, MDT and CDT timezones and it worked really well.Thanks Guys!!!

来源：https://stackoverflow.com/questions/11738992/java-set-timezone-at-runtime

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