Fix date calculation

aleksis/apps/alsijil/frontend/components/documentation/LessonInformation.vue

 <template>
   <v-card-text>
-    {{ $d(documentation.dateTimeStart, "shortTime") }} –
-    {{ $d(documentation.dateTimeEnd, "shortTime") }}
+    {{ $d(toDateTime(documentation.datetimeStart), "shortTime") }} –
+    {{ $d(toDateTime(documentation.datetimeEnd), "shortTime") }}
     <subject-chip :subject="documentation.subject" />
   </v-card-text>
 </template>
 
 <script>
 import SubjectChip from "aleksis.apps.cursus/components/SubjectChip.vue";
+import { DateTime } from "luxon";
 
 export default {
   name: "LessonInformation",
@@ -20,5 +21,10 @@ export default {
       required: true,
     },
   },
+  methods: {
+    toDateTime(dateString) {
+      return DateTime.fromISO(dateString);
+    },
+  },
 };
 </script>