diff --git a/src/routes/uonetplus-wiadomosciplus.js b/src/routes/uonetplus-wiadomosciplus.js
index 28eca2f..1032133 100644
--- a/src/routes/uonetplus-wiadomosciplus.js
+++ b/src/routes/uonetplus-wiadomosciplus.js
@@ -1,6 +1,7 @@
 const express = require('express');
 const router = express.Router();
 const protocol = require('../utils/connection');
+const {timestampToIsoTzFormat} = require('../utils/converter');
 const {fromString} = require('uuidv4');
 
 router.get("/", (req, res) => {
@@ -42,7 +43,7 @@ router.get([
             "apiGlobalKey": fromString(item.WiadomoscId.toString()),
             "korespondenci": item.Nadawca + " - P - (123456)",
             "temat": item.Tytul,
-            "data": new Date(item.DataWyslaniaUnixEpoch * 1000).toISOString(),
+            "data": timestampToIsoTzFormat(item.DataWyslaniaUnixEpoch),
             "skrzynka": "Jan Kowalski - U - (123456)",
             "hasZalaczniki": true,
             "przeczytana": !!item.GodzinaPrzeczytania,
@@ -63,7 +64,7 @@ router.get([
             "apiGlobalKey": fromString(item.WiadomoscId.toString()),
             "korespondenci": item.Nadawca + " - P - (123456)",
             "temat": item.Tytul,
-            "data": new Date(item.DataWyslaniaUnixEpoch * 1000).toISOString(),
+            "data": timestampToIsoTzFormat(item.DataWyslaniaUnixEpoch),
             "skrzynka": "Jan Kowalski - U - (123456)",
             "hasZalaczniki": true,
             "przeczytana": !!item.GodzinaPrzeczytania,
@@ -84,7 +85,7 @@ router.get([
             "apiGlobalKey": fromString(item.WiadomoscId.toString()),
             "korespondenci": item.Nadawca + " - P - (123456)",
             "temat": item.Tytul,
-            "data": new Date(item.DataWyslaniaUnixEpoch * 1000).toISOString(),
+            "data": timestampToIsoTzFormat(item.DataWyslaniaUnixEpoch),
             "skrzynka": "Jan Kowalski - U - (123456)",
             "hasZalaczniki": true,
             "przeczytana": !!item.GodzinaPrzeczytania,
@@ -110,7 +111,7 @@ router.get("/api/Skrzynki", (req, res) => {
 router.all("/api/WiadomoscSzczegoly", (req, res) => {
     const message = require("../../data/api/messages/WiadomosciOdebrane")[0];
     res.json({
-        "data": new Date(message.DataWyslaniaUnixEpoch * 1000).toISOString(),
+        "data": timestampToIsoTzFormat(message.DataWyslaniaUnixEpoch),
         "apiGlobalKey": fromString(message.WiadomoscId.toString()),
         "nadawca": "Natalia Wrzesień - P - (123456)",
         "odbiorcy": ["Jan kowalski - U - (123456)"],
@@ -139,7 +140,7 @@ router.all("/api/WiadomoscOdpowiedzPrzekaz", (req, res) => {
     const user = require("../../data/api/ListaUczniow")[1];
     const message = require("../../data/api/messages/WiadomosciOdebrane")[0];
     res.json({
-        "data": new Date(message.DataWyslaniaUnixEpoch * 1000).toISOString(),
+        "data": timestampToIsoTzFormat(message.DataWyslaniaUnixEpoch),
         "apiGlobalKey": fromString(message.WiadomoscId.toString()),
         "uzytkownikSkrzynkaGlobalKey": fromString(user.Id.toString()),
         "nadawcaSkrzynkaGlobalKey": fromString(message.NadawcaId.toString()),
diff --git a/src/utils/converter.js b/src/utils/converter.js
index 0a15a70..506fc23 100644
--- a/src/utils/converter.js
+++ b/src/utils/converter.js
@@ -1,4 +1,4 @@
-const { addDays, toDate } = require('date-fns');
+const { addDays, toDate, format} = require('date-fns');
 const WEEK_TICK = 6048000000000;
 const DAY_TICK = 864000000000;
 
@@ -32,6 +32,10 @@ function formatDate(today, iso = false) {
     return `${dd}.${mm}.${yyyy}`;
 }
 
+function timestampToIsoTzFormat(timestamp) {
+    return format(new Date(timestamp * 1000), 'yyyy-MM-dd\'T\'HH:mm:ss.SSXXX');
+}
+
 function getMonday(date) {
     let day = date.getDate() - date.getDay() + 1;
     return new Date(date.getFullYear(), date.getMonth(), day);
@@ -91,3 +95,4 @@ exports.getNextDayTick = getNextDayTick;
 exports.getPrevWeekTick = getPrevWeekTick;
 exports.getNextWeekTick = getNextWeekTick;
 exports.formatDate = formatDate;
+exports.timestampToIsoTzFormat = timestampToIsoTzFormat;