Actually lets do it like this

src/widgets/vikunja/component.jsx

@@ -28,9 +28,8 @@ export default function Component({ service }) {
 
   const projects = projectsData.filter((project) => project.id > 0); // saved filters have id < 0
 
-  const vikunjaDefaultDueDate = new Date("0001-01-01T00:00:00Z");
   const oneWeekFromNow = new Date(Date.now() + 7 * 24 * 60 * 60 * 1000);
-  const tasksWithDueDate = tasksData.filter((task) => new Date(task.dueDate) > vikunjaDefaultDueDate);
+  const tasksWithDueDate = tasksData.filter((task) => !task.dueDateIsDefault);
   const tasks7d = tasksWithDueDate.filter((task) => new Date(task.dueDate) <= oneWeekFromNow);
   const tasksOverdue = tasksWithDueDate.filter((task) => new Date(task.dueDate) <= new Date(Date.now()));
   const tasksInProgress = tasksData.filter((task) => task.inProgress);
@@ -44,7 +43,7 @@ export default function Component({ service }) {
         <Block label="vikunja.tasksInProgress" value={t("common.number", { value: tasksInProgress.length })} />
       </Container>
       {widget.enableTaskList &&
-        tasksWithDueDate.slice(0, 5).map((task) => (
+        tasksData.slice(0, 5).map((task) => (
           <div
             key={task.id}
             className="text-theme-700 dark:text-theme-200 relative h-5 rounded-md bg-theme-200/50 dark:bg-theme-900/20 m-1 px-1 flex"
@@ -54,12 +53,14 @@ export default function Component({ service }) {
                 {task.title}
               </div>
             </div>
-            <div className="self-center text-xs flex justify-end mr-1.5 pl-1 z-10 text-ellipsis overflow-hidden whitespace-nowrap">
-              {t("common.relativeDate", {
-                value: task.dueDate,
-                formatParams: { value: { style: "narrow", numeric: "auto" } },
-              })}
-            </div>
+            {!task.dueDateIsDefault && (
+              <div className="self-center text-xs flex justify-end mr-1.5 pl-1 z-10 text-ellipsis overflow-hidden whitespace-nowrap">
+                {t("common.relativeDate", {
+                  value: task.dueDate,
+                  formatParams: { value: { style: "narrow", numeric: "auto" } },
+                })}
+              </div>
+            )}
           </div>
         ))}
     </>

src/widgets/vikunja/widget.js

@@ -17,6 +17,7 @@ const widget = {
           title: task.title,
           priority: task.priority,
           dueDate: task.due_date,
+          dueDateIsDefault: task.due_date === "0001-01-01T00:00:00Z",
           inProgress: task.percent_done > 0 && task.percent_done < 1,
         })),
     },