@Entity
@Customizer(Cust.class)
public class MyEntity {
...

      <property name="eclipselink.descriptor.customizer.NewEntity" value="<pkg>.Cust"/>

public class Cust implements DescriptorCustomizer {

    @Override
    public void customize(ClassDescriptor cd) throws Exception {
        //TODO: error handling
        TimestampLockingPolicy tlp = (TimestampLockingPolicy) cd.getOptimisticLockingPolicy();
        tlp.useLocalTime();
    }   
}