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ZonedDateTime not serialised as UTC by default altough ObjectMapper Javadocs claiming UTC is the default #303
Description
As stated in the Jackson ObjectMapper the default should be UTC for writing Json:
/**
* Method for overriding default TimeZone to use for formatting.
* Default value used is UTC (NOT default TimeZone of JVM).
*/
public ObjectMapper setTimeZone(TimeZone tz) {
_deserializationConfig = _deserializationConfig.with(tz);
_serializationConfig = _serializationConfig.with(tz);
return this;
}
/**
* Base settings contain defaults used for all {@link ObjectMapper}
* instances.
*/
protected final static BaseSettings DEFAULT_BASE = new BaseSettings(
null, // cannot share global ClassIntrospector any more (2.5+)
DEFAULT_ANNOTATION_INTROSPECTOR,
null, TypeFactory.defaultInstance(),
null, StdDateFormat.instance, null,
Locale.getDefault(),
null, // to indicate "use Jackson default TimeZone" (UTC since Jackson 2.7)
Base64Variants.getDefaultVariant(),
// Only for 2.x; 3.x will use more restrictive default
LaissezFaireSubTypeValidator.instance,
// Since 2.12:
new DefaultAccessorNamingStrategy.Provider(),
// Since 2.16: [databind#2502] Add a way to configure Caches Jackson uses
DefaultCacheProvider.defaultInstance()
);
With the java 8 time module when the timezone is set to null no time zone information is used on serialisation as the provider.getConfig().hasExplicitTimeZone() does result in false if the default of null is set. So ZonedDateTime is not written with utc as default.
Is this expected behavior to not overwrite the TimeZone defined in the ZonedDateTime? Than this should be properly Documented.
Minimal example:
ObjectMapper testmapper = new ObjectMapper();
testmapper.registerModule(new JavaTimeModule());
testmapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
ZonedDateTime testtime = ZonedDateTime.now(ZoneId.of("Europe/Berlin"));
String teststring = testmapper.writeValueAsString(testtime);
// 2024-02-20T11:37:42.009045+01:00
testmapper = new ObjectMapper();
testmapper.registerModule(new JavaTimeModule());
testmapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
testmapper.setTimeZone(TimeZone.getTimeZone("UTC"));
testtime = ZonedDateTime.now(ZoneId.of("Europe/Berlin"));
teststring = testmapper.writeValueAsString(testtime);
// 2024-02-20T10:38:13.0324177Z
Activity
cowtowncoder commentedon Feb 28, 2024
Quick note: I think (but cannot canonically claim as the official answer) that the default
TimeZoneis only meant to be used in absence of explicit one; at least with default settings.However. Since you mention
WRITE_DATES_WITH_CONTEXT_TIME_ZONE, enabling that... oh.It does look like it should be enabled since 2.13.
(as the background this default timezone was most useful for
java.util.Date, instances of which do not have timezone specified and must use something if serialized as String value).So maybe this is indeed working incorrectly. But aside from fixing this (and testing properly), there is then the question of backwards-compatibility -- I think this might be acceptable for a minor version (even if others might argue otherwise). But would need to be considered carefully.
cowtowncoder commentedon Mar 26, 2025
--Ok, yes, I think behavior is correct:
ZonedDateTime's Time zone should not be overwritten by default.--EDIT: I agree this is confusing; although default is UTC, that is not taken into account in this particular case, due to default timezone being implicit, not explicit.
But due to backwards-compatibility aspects, I think behavior needs to remain as-is. I am open to suggestions on how to change Javadocs.
[-]ZonedDateTime not serialised as UTC by default[/-][+]`ZonedDateTime` not serialised as UTC by default altough ObjectMapper Javadocs claiming UTC is the default[/+]AzazelSensei commentedon Sep 21, 2026
Opened #390 with the javadoc/README note on implicit UTC vs ZonedDateTime.
Document implicit UTC vs ZonedDateTime serialization #303 (#390)