Extend Exception instead of Throwable

core/src/main/java/se/su/dsv/scipro/report/DuplicateDateException.java

@@ -4,7 +4,7 @@ import se.su.dsv.scipro.system.ProjectType;
 
 import java.time.LocalDate;
 
-public class DuplicateDateException extends Throwable {
+public class DuplicateDateException extends Exception {
     private final LocalDate validFrom;
     private final ProjectType projectType;