How to list the timezone offset, timezone ID, and long name in Joda Time / Java 8?

Question

Time zone ids of Joda Time can simply be displayed with the following segment of code.

Set<String> zoneIds = DateTimeZone.getAvailableIDs();

for(String zoneId:zoneIds) {
    System.out.println(zoneId);
}

But how to display the corresponding timezone offset, timezone ID, and long name so that the list could look something like the following?

(GMT-10:00) Pacific/Honolulu, Hawaii Standard Time
(GMT-10:00) Pacific/Johnston, Hawaii Standard Time
(GMT-10:00) Pacific/Fakaofo, Tokelau Time
(GMT-10:00) HST, Hawaii Standard Time

They are needed to list in a drop-down-box for selection.

---

The following snippet shows the names but the offset it displays looks wonky.

Set<String> zoneIds = DateTimeZone.getAvailableIDs();

for (String zoneId : zoneIds) {
    int offset = DateTimeZone.forID(zoneId).getOffset(new DateTime());
    String longName = TimeZone.getTimeZone(zoneId).getDisplayName();

    System.out.println("(" + offset + ") " + zoneId + ", " + longName);
}

Out of the long list it displays, a few of them are shown like,

(-36000000) Pacific/Honolulu, Hawaii Standard Time
(-36000000) Pacific/Johnston, Hawaii Standard Time
(-36000000) Pacific/Fakaofo, Tokelau Time
(-36000000) HST, Hawaii Standard Time

The offset should be as shown in this list.

Answer 1

The following approach worked.

import java.util.Set;
import java.util.TimeZone;
import org.joda.time.DateTimeZone;
import org.joda.time.format.DateTimeFormat;
import org.joda.time.format.DateTimeFormatter;

Set<String> zoneIds = DateTimeZone.getAvailableIDs();
DateTimeFormatter dateTimeFormatter = DateTimeFormat.forPattern("ZZ");

for (String zoneId : zoneIds) {
    String offset = dateTimeFormatter.withZone(DateTimeZone.forID(zoneId)).print(0);
    String longName = TimeZone.getTimeZone(zoneId).getDisplayName();

    System.out.println("(" + offset + ") " + zoneId + ", " + longName);
}

There could also be other and probably better ways that I'm right now unaware of.

---

Or

import java.util.Set;
import org.joda.time.DateTimeUtils;
import org.joda.time.DateTimeZone;
import org.joda.time.format.DateTimeFormat;
import org.joda.time.format.DateTimeFormatter;

Set<String> zoneIds = DateTimeZone.getAvailableIDs();
DateTimeFormatter dateTimeFormatter = DateTimeFormat.forPattern("ZZ");

for (String zoneId : zoneIds) {
    String offset = dateTimeFormatter.withZone(DateTimeZone.forID(zoneId)).print(0);
    String longName = DateTimeZone.forID(zoneId).getName(DateTimeUtils.currentTimeMillis());

    System.out.println("(" + offset + ") " + zoneId + ", " + longName);
}

For Greenwich Mean Time (Etc/GMT+0, for example), it would display, for example +00:00 instead of displaying GMT+00:00 as in the first case.

If the name is not available for the locale, then this method (public final String getName(long instant)) returns a string in the format [+-]hh:mm.

An appropriate Locale can also be used, if needed using the overloaded method,

public String getName(long instant, Locale locale)

---

Short names, for example UTC for Coordinated Universal Time can be displayed as follows.

import java.util.Set;
import org.joda.time.DateTimeUtils;
import org.joda.time.DateTimeZone;
import org.joda.time.format.DateTimeFormat;
import org.joda.time.format.DateTimeFormatter;

Set<String> zoneIds = DateTimeZone.getAvailableIDs();
DateTimeFormatter dateTimeFormatter = DateTimeFormat.forPattern("ZZ");

for (String zoneId : zoneIds) {
    String offset = dateTimeFormatter.withZone(DateTimeZone.forID(zoneId)).print(0);
    String shortName = DateTimeZone.forID(zoneId).getShortName(DateTimeUtils.currentTimeMillis());

    System.out.println("(" + offset + ") " + zoneId + ", " + shortName);
}

With an appropriate Locale, if needed using the overloaded method,

public String getShortName(long instant, Locale locale)

---

Update :

Using the Java Time API in Java SE 8 in which this is further simplified.

import java.time.ZoneId;
import java.time.ZoneOffset;
import java.time.ZonedDateTime;
import java.time.format.TextStyle;
import java.util.Locale;
import java.util.Set;

Set<String> zoneIds = ZoneId.getAvailableZoneIds();

for (String zoneId : zoneIds) {
    ZoneId zone = ZoneId.of(zoneId);
    ZonedDateTime zonedDateTime = ZonedDateTime.now(zone);

    ZoneOffset offset = zonedDateTime.getOffset();
    String longName = zone.getDisplayName(TextStyle.FULL, Locale.ENGLISH);

    System.out.println("(" + offset + ") " + zoneId + ", " + longName);
}

The display name has various styles available in java.time.format.TextStyle. For example, abbreviations can be displayed using TextStyle.SHORT.

zone.getDisplayName(TextStyle.FULL, Locale.ENGLISH) will display long names like "India Time". This is however, not a full name unlike Joda Time.

The following will display a full name of the given name like "India Standard Time" (wherever applicable).

DateTimeFormatter pattern = DateTimeFormatter.ofPattern("zzzz");
String longName = pattern.format(ZonedDateTime.now(ZoneId.of(zoneId)));

The following will display a zone-offset of the given zone like GMT+05:30 (note the capitalization of the pattern).

DateTimeFormatter pattern = DateTimeFormatter.ofPattern("ZZZZ");
String longName = pattern.format(ZonedDateTime.now(ZoneId.of(zoneId)));

The following is for displaying abbreviations.

DateTimeFormatter pattern = DateTimeFormatter.ofPattern("zzz");
String longName = pattern.format(ZonedDateTime.now(ZoneId.of(zoneId)));

Capital ZZZ for zone-offset like +0530, +0000.

https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html

Answer 2

import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.time.format.TextStyle;
import java.time.zone.ZoneRules;
import java.util.Locale;
import java.util.TimeZone;

// Europe/Berlin
// Europe/London
// Asia/Kolkata
public class TimeZoneTest {

    public static void main(String[] args) {

        ZonedDateTime timeZone = ZonedDateTime.of(LocalDateTime.of(2020, 8, 06, 05, 45),
                                                   ZoneId.of("Asia/Manila"));

        Instant instant = timeZone.toInstant();
        ZoneRules rules = timeZone.getZone().getRules();
        boolean isDst = rules.isDaylightSavings(instant);
        String dstShortName = DateTimeFormatter.ofPattern("zzz").format(timeZone);
        String dstLongName = DateTimeFormatter.ofPattern("zzzz").format(timeZone);
        TimeZone tz = TimeZone.getTimeZone(timeZone.getZone());

        System.out.println(timeZone.getZone().getId());
        System.out.println(timeZone.getOffset().getTotalSeconds()); //Offset
        System.out.println(rules.getStandardOffset(instant).getTotalSeconds()); //RawOffset
        System.out.println((rules.getDaylightSavings(instant).getSeconds())); //DstSavings
        System.out.println(rules.isDaylightSavings(instant));
        System.out.println(dstShortName);
        System.out.println(dstLongName);
        if (isDst) {
            //Set standard timezone name
            System.out.println(timeZone.getZone().getDisplayName(TextStyle.SHORT, Locale.ENGLISH));
            System.out.println(timeZone.getZone().getDisplayName(TextStyle.FULL, Locale.ENGLISH));
        } else {
            //Set DST timezone name
            System.out.println(tz.getDisplayName(true, TimeZone.SHORT, Locale.ENGLISH));
            System.out.println(tz.getDisplayName(true, TimeZone.LONG, Locale.ENGLISH));
        }

//        //SHORT: CEST
//        DateTimeFormatter.ofPattern("zzz").format(zonedDateTime)
//
//        //SHORT: CET 
//        ZoneId.getDisplayName(TextStyle.SHORT,Locale.ENGLISH)
//
//        //LONG: Central European Summer Time
//        DateTimeFormatter.ofPattern("zzzz").format(zonedDateTime)
//
//        //LONG: Central European Time
//        ZoneId.getDisplayName(TextStyle.LONG,Locale.ENGLISH)
//
//        //Use this for converting CET to CEST and vice versa
//        TimeZone tz = TimeZone.getTimeZone(timeZone.getZone());
//        tz.getDisplayName(true, TimeZone.SHORT, Locale.ENGLISH));


//Joda
//        DateTimeZone dz = DateTimeZone.forID("Asia/Manila");
//        String shortName = dz.getShortName(DateTimeUtils.currentTimeMillis());
//        System.out.println(shortName);
//
//        String longerName = dz.getName(DateTimeUtils.currentTimeMillis());
//        System.out.println(longerName);
    }
}