How to translate between windows and IANA timezones in java

Question

I need to translate between IANA timezone & windows timezone & vice-versa. There is another question reported: How to translate between Windows and IANA time zones?

It specifies that Noda time library can be used in .Net

Do we have any library to be used in Java? Or any other utility to be used in java?

Answer 1

This may be what you need, but I don't know if it will work for all your use cases:

for (String tzId : TimeZone.getAvailableIDs()) {
  TimeZone tz = TimeZone.getTimeZone(tzId);
  if (tz.getDisplayName(Locale.ENGLISH).equals("Eastern Standard Time")) {
    System.out.println("tz = " + tzId);
  }
}

Answer 2

I have implemented support for Windows zones in my Java-library Time4J. The last version v4.2 is also interoperable with Java-8 so it is easy to convert all basic Time4J-types to java.time-equivalents. For example recognizing Windows zones as strings is possible in constructing as well as during parsing:

  // conversion Windows to IANA
  WindowsZone wzn = WindowsZone.of("Eastern Standard Time");
  TZID winzone = wzn.resolveSmart(Locale.US);
  System.out.println(winzone.canonical()); // WINDOWS~America/New_York

  // usage in timezone calculation
  Timezone tz = Timezone.of(winzone);
  System.out.println(Moment.UNIX_EPOCH.toZonalTimestamp(winzone)); // 1969-12-31T19

  // usage in parsing and formatting
  ChronoFormatter<Moment> f =
    ChronoFormatter.ofMomentPattern(
      "MM/dd/uuuu hh:mm a zzzz", PatternType.CLDR, Locale.US, winzone);
  Moment pacificTime = f.parse("07/17/2015 02:45 PM Pacific Standard Time");
  System.out.println(f.format(pacificTime)); // 07/17/2015 05:45 PM Eastern Standard Time

As you can see, a locale Information is necessary to map a Windows zone like "Eastern Standard Time" to an Olson/IANA-identifier like "America/New_York". The underlying data and mapping informations are taken from CLDR.

The reverse way from IANA to Windows might be done this simple way:

String iana = "America/New_York";
String winzone = "WINDOWS~" + iana;
NameStyle dummy = NameStyle.LONG_STANDARD_TIME; // does not really matter
String name = Timezone.of(winzone).getDisplayName(dummy, Locale.US);
System.out.println(name); // Eastern Standard Time

However, this reverse conversion might not work for all iana-identifiers because Windows only supports a very simplified subset of timezones compared with IANA-TZDB. I also think that the reverse way is hardly used in practice. Users should rather work with IANA-timezones by default and only use Windows timezones if that is the (unavoidable) input to handle (see first part of my answer).