junit-team/junit5 · error · ExtensionConfigurationException

@DefaultTimeZone not configured correctly. Could not find…

Error message

@DefaultTimeZone not configured correctly.
Could not find the specified time zone + '%s'.
Please use correct identifiers, e.g. "GMT" for Greenwich Mean Time.

What it means

ExtensionConfigurationException from DefaultTimeZoneExtension.createTimeZoneFromZoneId, thrown when the supplied zone id is unrecognized. Because TimeZone.getTimeZone silently falls back to GMT for unknown ids, JUnit explicitly checks: if the resolved zone equals GMT but the requested id was not literally "GMT", the id is treated as invalid and rejected.

Solutions

  1. Use a valid IANA zone id, e.g. "America/New_York", "Europe/Berlin", "UTC".
  2. Confirm the id via java.time.ZoneId.getAvailableZoneIds() if unsure.
  3. Avoid deprecated three-letter ids; prefer the canonical IANA names.

Example fix

// before
@DefaultTimeZone("EST")
void test() {}
// after
@DefaultTimeZone("America/New_York")
void test() {}
Defensive patterns

Strategy: validation

Validate before calling

String id = annotation.value();
if (!ZoneId.getAvailableZoneIds().contains(id)) { /* not a valid IANA id */ }

Type guard

static boolean isValidZoneId(String id) {
    return ZoneId.getAvailableZoneIds().contains(id);
}

Prevention

When it happens

Trigger: Annotating with @DefaultTimeZone("US/Eastern") (Java uses "America/New_York" — wrong id), or a typo like @DefaultTimeZone("UTSC"), or any string TimeZone.getTimeZone cannot map. The equals-GMT-but-not-GMT branch fires.

Common situations: Using the legacy three-letter ids ("EST", "PST") which are deprecated/ambiguous; typos; copying an IANA id that the JVM's tz database doesn't have; regional shorthand that isn't a real zone.

Related errors

AI-assisted analysis of junit-team/junit5@f070c699a0 (2026-08-11). Data as JSON: /api/errors/2cdf42c211c54ef0. Report an issue: GitHub.

Appendix: source

Thrown at junit-jupiter-api/src/main/java/org/junit/jupiter/api/util/DefaultTimeZoneExtension.java:83

			return createTimeZoneFromProvider(annotation.timeZoneProvider());
		}
	}

	private static void validateCorrectConfiguration(DefaultTimeZone annotation) {
		boolean noValue = annotation.value().isEmpty();
		boolean noProvider = annotation.timeZoneProvider() == NullTimeZoneProvider.class;
		if (noValue == noProvider) {
			throw new ExtensionConfigurationException(
				"Either a valid time zone id or a TimeZoneProvider must be provided to "
						+ DefaultTimeZone.class.getSimpleName());
		}
	}

	private static TimeZone createTimeZoneFromZoneId(String timeZoneId) {
		TimeZone configuredTimeZone = TimeZone.getTimeZone(timeZoneId);
		// TimeZone::getTimeZone returns with GMT as fallback if the given ID cannot be understood
		if (configuredTimeZone.equals(TimeZone.getTimeZone("GMT")) && !"GMT".equals(timeZoneId)) {
			throw new ExtensionConfigurationException("""
					@DefaultTimeZone not configured correctly.
					Could not find the specified time zone + '%s'.
					Please use correct identifiers, e.g. "GMT" for Greenwich Mean Time.
					""".formatted(timeZoneId));
		}
		return configuredTimeZone;
	}

	private static TimeZone createTimeZoneFromProvider(Class<? extends TimeZoneProvider> providerClass) {
		try {
			TimeZoneProvider provider = ReflectionSupport.newInstance(providerClass);
			return Optional.ofNullable(provider.get()).orElse(TimeZone.getTimeZone("GMT"));
		}
		catch (Exception exception) {
			throw new ExtensionConfigurationException("Could not instantiate TimeZoneProvider because of exception",
				exception);
		}
	}

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