In this commit, for DateTimeSerializer: https://github.com/FasterXML/jackson-datatype-joda/commit/cf2f4c282c3eb4048ca501e6af21948afb447913#diff-86756f80e06fe3b0a847c963534b14baR55 `DateTime.parse()` is replaced by using the `JacksonJodaDateFormat`, which defaults to `FormatConfig.DEFAULT_DATETIME_FORMAT`, which is defined as `new JacksonJodaDateFormat(ISODateTimeFormat.dateTime().withZoneUTC())`. `DateTime.parse()` uses `ISODateTimeFormat.dateTimeParser().withOffsetParsed()`: http://www.joda.org/joda-time/apidocs/org/joda/time/DateTime.html#parse-java.lang.String- So ultimately, the default date time parser format has changed from `ISODateTimeFormat.dateTimeParser()` to `ISODateTimeFormat.dateTime()`. Although similar, `ISODateTimeFormat.dateTimeParser()` is much less restrictive: http://www.joda.org/joda-time/apidocs/org/joda/time/format/ISODateTimeFormat.html#dateTime-- http://www.joda.org/joda-time/apidocs/org/joda/time/format/ISODateTimeFormat.html#dateTimeParser-- As an example, the datetime "2015-07-27T08:11:07-07:00" is missing the `.SSS` milliseconds value, so it fails in 2.6.0 but works in 2.5.4: ``` Caused by: java.lang.IllegalArgumentException: Invalid format: "2015-07-27T08:11:07-07:00" is malformed at "-07:00" at org.joda.time.format.DateTimeFormatter.parseDateTime(DateTimeFormatter.java:899) ~[joda-time-2.8.1.jar:2.8.1] at com.fasterxml.jackson.datatype.joda.deser.DateTimeDeserializer.deserialize(DateTimeDeserializer.java:90) ~[jackson-datatype-joda-2.6.0.jar:2.6.0] at com.fasterxml.jackson.datatype.joda.deser.DateTimeDeserializer.deserialize(DateTimeDeserializer.java:22) ~[jackson-datatype-joda-2.6.0.jar:2.6.0] at com.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:520) ~[jackson-databind-2.6.0.jar:2.6.0] at com.fasterxml.jackson.databind.deser.impl.FieldProperty.deserializeAndSet(FieldProperty.java:101) ~[jackson-databind-2.6.0.jar:2.6.0] at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:256) ~[jackson-databind-2.6.0.jar:2.6.0] ``` A workaround in this situation is to add a `@JsonFormat` annotation to the property specifying the specific format, e.g: `@JsonFormat(pattern="yyyy-MM-dd'T'HH:mm:ssZZ")`