Please refer to ZonedDateTime in the JSR 310 (JDK 1.8 time API) documentation:

http://threeten.sourceforge.net/apidocs/javax/time/calendar/ZonedDateTime.html

OData does not permit such a value (essentially a DateTimeOffset together with a named time zone region) to be represented except by using string or complex types.

We might reasonably expect that OData interoperability with the new Java time system will be impacted by the omission of a corresponding CSDL primitive type.