Java 8 time zone ZoneRulesException: Unknown time-zone ID: EST

Question

"EST" is one of the timeZone id from TimeZone.getAvailableIDs();

but

TimeZone.getAvailableIDs();  // contains EST
ZoneId.of("EST")

java.time.zone.ZoneRulesException: Unknown time-zone ID: EST

Answer 1

Try this:

ZoneId.of("EST", ZoneId.SHORT_IDS);

Explanation: ZoneID.SHORT_IDS maps deprecated 3-letter codes to regular ones and for some reason it must be specified explicitely to take effect.

From JDK javadoc: "Use of short zone IDs has been deprecated in TimeZone".

Answer 2

You are mixing old and new API's.

TimeZone.getAvailableIDs() returns Time Zone ID's that TimeZone.getTimeZone(String ID) can resolve.

ZoneId.getAvailableZoneIds() returns Zone ID's that ZoneId.of(String zoneId) can resolve.

If you compare the results of the 2, you will see:

public static void main(String[] args) {
    Set<String> timeZones = Set.of(TimeZone.getAvailableIDs());
    Set<String> zoneIds = ZoneId.getAvailableZoneIds();
    System.out.println("Extra TimeZone's: " + diff(timeZones, zoneIds));
    System.out.println("Extra ZoneId's: " + diff(zoneIds, timeZones));
}
static Set<String> diff(Set<String> a, Set<String> b) {
    Set<String> diff = new TreeSet<>(a);
    diff.removeAll(b);
    return diff;
}

Output (jdk-11.0.1)

Extra TimeZone's: [ACT, AET, AGT, ART, AST, BET, BST, CAT, CNT, CST, CTT, EAT, ECT, EST, HST, IET, IST, JST, MIT, MST, NET, NST, PLT, PNT, PRT, PST, SST, VST]
Extra ZoneId's: []

As you can see, ZoneId.getAvailableZoneIds() does not claim to support EST, only TimeZone.getAvailableIDs() does.