diff --git a/app/components/troi.client.tsx b/app/components/troi.client.tsx
index d4063e0c..c6607adb 100644
--- a/app/components/troi.client.tsx
+++ b/app/components/troi.client.tsx
@@ -12,6 +12,8 @@ import {
 import moment from "moment";
 import { TimeEntries, TimeEntry } from "~/troi/TimeEntry";
 import { CalculationPosition } from "~/troi/CalculationPosition";
+import { useFetcher } from "@remix-run/react";
+import { convertToCacheFormat } from "~/utils/TimeEntryCache";
 
 interface Props {
   username: string;
@@ -71,21 +73,25 @@ export default function Troi(props: Props) {
     selectedDate,
   );
 
+  const fetcher = useFetcher();
+
   async function onAddEntryClicked(
     position: CalculationPosition,
     hours: number,
     description: string,
   ) {
-    // await troiController?.addEntry(
-    //   selectedDate,
-    //   position,
-    //   hours,
-    //   description,
-    //   () => {}
-    // );
-    // troiController?.getEntriesFor(selectedDate).then((entries) => {
-    //   setEntriesForSelectedDate(entries);
-    // });
+    fetcher.submit(
+      {
+        hours,
+        description,
+      },
+      {
+        method: "POST",
+        action: `/calculation_postions/${
+          position.id
+        }/time_entries/${convertToCacheFormat(selectedDate)}`,
+      },
+    );
   }
 
   async function onUpdateEntryClicked(
@@ -98,12 +104,7 @@ export default function Troi(props: Props) {
     // });
   }
 
-  async function onDeleteEntryClicked(entry: TimeEntry, positionId: number) {
-    // await troiController?.deleteEntry(entry, positionId, () => {});
-    // troiController?.getEntriesFor(selectedDate).then((entries) => {
-    //   setEntriesForSelectedDate(entries);
-    // });
-  }
+  async function onDeleteEntryClicked(entry: TimeEntry, positionId: number) {}
 
   return (
     <div>
diff --git a/app/routes/calculation_postions.$calculationPositionId.time_entries.$date.tsx b/app/routes/calculation_postions.$calculationPositionId.time_entries.$date.tsx
new file mode 100644
index 00000000..1ea52ab1
--- /dev/null
+++ b/app/routes/calculation_postions.$calculationPositionId.time_entries.$date.tsx
@@ -0,0 +1,41 @@
+import { ActionFunctionArgs } from "@remix-run/node";
+import TroiApiService from "troi-library";
+import { login } from "~/cookies.server";
+import { addTimeEntry } from "~/troi/troiControllerServer";
+
+export async function action({ request, params }: ActionFunctionArgs) {
+  if (request.method !== "POST") {
+    throw new Error("MethodNotAllowed");
+    // todo (Malte Laukötter, 2023-12-15): throw a error with the correct error type (405)
+  }
+
+  if (params.calculationPositionId === undefined) {
+    throw new Error("Missing calculationPositionId");
+  }
+
+  if (params.date === undefined) {
+    throw new Error("Missing date");
+  }
+
+  const body = await request.formData();
+
+  const hours = body.get("hours");
+  if (typeof hours !== "string") {
+    throw new Error("Missing hours");
+  }
+
+  const description = body.get("description");
+  if (typeof description !== "string") {
+    throw new Error("Missing description");
+  }
+
+  addTimeEntry(
+    request,
+    parseInt(params.calculationPositionId, 10),
+    params.date,
+    parseFloat(hours),
+    description,
+  );
+
+  return;
+}
diff --git a/app/troi/troiControllerServer.ts b/app/troi/troiControllerServer.ts
index fa3a3a7b..bbf3e8e2 100644
--- a/app/troi/troiControllerServer.ts
+++ b/app/troi/troiControllerServer.ts
@@ -102,8 +102,14 @@ async function fetchCalculationPositionsAndSaveToSession(request: Request) {
         clientId: clientId.toString(),
         favoritesOnly: true.toString(),
       },
-    })) as any[]
-  ).map((obj: any) => ({
+    })) as {
+      Id: number;
+      DisplayPath: string;
+      Subproject: {
+        id: number;
+      };
+    }[]
+  ).map((obj) => ({
     name: obj.DisplayPath,
     id: obj.Id,
     subprojectId: obj.Subproject.id,
@@ -169,28 +175,37 @@ async function fetchTimeEntriesAndSaveToSession(request: Request) {
   const calculationPositions = await getCalculationPositions(request);
   const entries: TimeEntry[] = (
     await Promise.all(
-      calculationPositions.map((calcPos) =>
-        troiApi.makeRequest({
-          url: "/billings/hours",
-          params: {
-            clientId: clientId.toString(),
-            employeeId: employeeId.toString(),
-            calculationPositionId: calcPos.id.toString(),
-            startDate: formatDateToYYYYMMDD(addDaysToDate(new Date(), -366)),
-            endDate: formatDateToYYYYMMDD(addDaysToDate(new Date(), 366)),
-          },
-        }),
+      calculationPositions.map(
+        (calcPos) =>
+          troiApi.makeRequest({
+            url: "/billings/hours",
+            params: {
+              clientId: clientId.toString(),
+              employeeId: employeeId.toString(),
+              calculationPositionId: calcPos.id.toString(),
+              startDate: formatDateToYYYYMMDD(addDaysToDate(new Date(), -366)),
+              endDate: formatDateToYYYYMMDD(addDaysToDate(new Date(), 366)),
+            },
+          }) as Promise<{
+            id: number;
+            Date: string;
+            Quantity: string;
+            Remark: string;
+            CalculationPosition: {
+              id: number;
+            };
+          }>,
       ),
     )
   )
     .flat()
-    .map((e: any) => {
+    .map((entry) => {
       return {
-        id: e.id,
-        date: e.Date,
-        hours: e.Quantity,
-        description: e.Remark,
-        calculationPosition: e.CalculationPosition.id,
+        id: entry.id,
+        date: entry.Date,
+        hours: parseFloat(entry.Quantity),
+        description: entry.Remark,
+        calculationPosition: entry.CalculationPosition.id,
       };
     });
 
@@ -213,6 +228,50 @@ export async function getTimeEntries(request: Request): Promise<TimeEntries> {
   );
 }
 
+export async function addTimeEntry(
+  request: Request,
+  calculationPostionId: number,
+  date: string,
+  hours: number,
+  description: string,
+) {
+  const cookieHeader = request.headers.get("Cookie");
+  const session = await getSession(cookieHeader);
+
+  const troiApi = await getTroiApi(
+    session.get("username"),
+    session.get("troiPassword"),
+    await getClientId(request),
+    await getEmployeeId(request),
+  );
+
+  const result = (await troiApi.postTimeEntry(
+    calculationPostionId,
+    date,
+    hours,
+    description,
+  )) as {
+    id: number;
+    Name: string;
+    Quantity: string;
+  };
+
+  const existingEntries = session.get("troiTimeEntries");
+  if (existingEntries !== undefined) {
+    existingEntries[result.id] = {
+      id: result.id,
+      date: date,
+      hours: parseFloat(result.Quantity),
+      description: result.Name,
+      calculationPosition: calculationPostionId,
+    };
+  }
+
+  await commitSession(session);
+
+  return result;
+}
+
 /**
  * Return data from the session cache and revalidate cached data in the background.
  *