Why my LocalDate property is stored as a String?

I have a User class with field:

@Relationship(value = "HAS_VACATIONS", direction = OUTGOING)
private Set vacations;

In Vacations class I have some dates:

private LocalDate startDate;
private LocalDate endDate;

When I save a User, startDate and endDate are stored as java.lang.String in the graph.

I have a class Holiday with field:

private LocalDate date;

When I save a Holiday, date is stored as a java.time.LocalDate in the graph.

If I save Vacactions directly outside User, I have the same java.lang.String issue.

I there an OGM issue with mapping?

I assume that you are using an 3.2.x version of Neo4j-OGM, right? In this case you have to enable the native type conversion by adding the native-type dependency.

<dependency>
    <groupId>org.neo4j</groupId>
    <artifactId>neo4j-ogm-bolt-native-types</artifactId>
    <version>${your-neo4j-ogm.version}</version>
</dependency>

and actively enable it in the Neo4j-OGM configuration

Configuration configuration = new Configuration.Builder()
        // ...
        .useNativeTypes()
        .build()

The reason why this is a dedicated dependency is rooted in the missing functionality in Neo4j back in the days to handle date/time types.

More on this topic: Neo4j-OGM - Native property types

I'm using neo4j-ogm-quarkus 3.6.0 with neo4j-ogm-core 4.0.8.

For backward compatibility you still have to enable the native types for the Neo4j-OGM configuration.
This can be done via application.properties

org.neo4j.ogm.use-native-types = true

(reference: GitHub - neo4j/neo4j-ogm-quarkus: Quarkus extension to that allows proper usage of Neo4j-OGM inside Quarkus.)