Unresolved type LocalDate

I created a new Kotlin project using Intellij 2016.3.3 and importing java.time.LocalDate doesn’t do anything.
Using the type shows a Unsolved Type in the IDE.
Building the same class with a simple gradle script does work so this looks like a problem with the IDE.

Have I missed an obvious setting?

Check in the project structure, what the project SDK is. It should be set to Java 1.8, to be able to use its classes.

Thank you for the hint; I found the problem while looking around the project structure.

The SDK used was referenced as simply 1.8 (which is the name IntelliJ gave my installed JDK).
While in the SDKs tab, I noticed that 1.8 didn’t have any jars in its classpath.
Somehow, the path to the jdk dropped the version number and couldn’t be resolved.
Fixing the JDK home path solved my issues.