diff --git a/include/text_utils.h b/include/text_utils.h
new file mode 100644
index 0000000..3a1c768
--- /dev/null
+++ b/include/text_utils.h
@@ -0,0 +1,35 @@
+#pragma once
+#include <Arduino.h>
+
+// The M5Stack default font does not correctly render UTF-8 encoded German
+// umlauts (ä, ö, ü, ß), they show up as garbled characters or boxes.
+// This helper replaces them with their common ASCII transliteration
+// (ö -> oe, ä -> ae, ü -> ue, ß -> ss) before printing to the display.
+// This is the simplest, most robust fix without needing a custom font.
+inline String sanitizeGermanText(const String &input) {
+    String out;
+    out.reserve(input.length());
+
+    for (size_t i = 0; i < input.length(); i++) {
+        unsigned char c1 = input[i];
+
+        // UTF-8 two-byte sequences for German umlauts start with 0xC3
+        if (c1 == 0xC3 && i + 1 < input.length()) {
+            unsigned char c2 = input[i + 1];
+            switch (c2) {
+                case 0xA4: out += "ae"; i++; continue; // ä
+                case 0xB6: out += "oe"; i++; continue; // ö
+                case 0xBC: out += "ue"; i++; continue; // ü
+                case 0x84: out += "Ae"; i++; continue; // Ä
+                case 0x96: out += "Oe"; i++; continue; // Ö
+                case 0x9C: out += "Ue"; i++; continue; // Ü
+                case 0x9F: out += "ss"; i++; continue; // ß
+                default: break;
+            }
+        }
+
+        out += (char)c1;
+    }
+
+    return out;
+}
diff --git a/src/screens/calendar_detail_screen.cpp b/src/screens/calendar_detail_screen.cpp
index 990defd..23b0ac1 100644
--- a/src/screens/calendar_detail_screen.cpp
+++ b/src/screens/calendar_detail_screen.cpp
@@ -1,4 +1,5 @@
 #include "calendar_detail_screen.h"
+#include "../../include/text_utils.h"
 #include <M5Stack.h>
 #include "../../include/theme.h"
 #include "../icons/icons.h"
@@ -50,7 +51,7 @@ void renderCalendarDetailScreen(bool forceRefresh) {
         M5.Lcd.setTextColor(Theme::TEXT, Theme::BG);
         M5.Lcd.setTextSize(1);
         M5.Lcd.setCursor(10, y);
-        M5.Lcd.print(ev.summary.substring(0, 28));
+        M5.Lcd.print(sanitizeGermanText(ev.summary.substring(0, 28)));
 
         M5.Lcd.setTextColor(Theme::TEXT_DIM, Theme::BG);
         M5.Lcd.setCursor(230, y);
diff --git a/src/screens/home_screen.cpp b/src/screens/home_screen.cpp
index fd516c8..f5dc559 100644
--- a/src/screens/home_screen.cpp
+++ b/src/screens/home_screen.cpp
@@ -1,4 +1,5 @@
 #include "home_screen.h"
+#include "../../include/text_utils.h"
 #include <M5Stack.h>
 #include "../../include/theme.h"
 #include "../icons/icons.h"
@@ -75,7 +76,7 @@ void renderHomeScreen(bool forceRefresh) {
         M5.Lcd.setTextSize(2);
         M5.Lcd.setTextColor(Theme::TEXT_DIM, Theme::BG);
         M5.Lcd.setCursor(90, 65);
-        M5.Lcd.print(lastWeather.current.description);
+        M5.Lcd.print(sanitizeGermanText(lastWeather.current.description));
 
         if (willRainSoon(lastWeather, 8)) {
             Icons::drawRainWarning(280, 30);
@@ -106,7 +107,7 @@ void renderHomeScreen(bool forceRefresh) {
             M5.Lcd.setTextColor(Theme::TEXT, Theme::BG);
             M5.Lcd.setTextSize(2);
             M5.Lcd.setCursor(10, y);
-            M5.Lcd.print(ev.summary.substring(0, 20));
+            M5.Lcd.print(sanitizeGermanText(ev.summary.substring(0, 20)));
 
             M5.Lcd.setTextColor(Theme::TEXT_DIM, Theme::BG);
             M5.Lcd.setTextSize(1);
diff --git a/src/screens/mvg_screen.cpp b/src/screens/mvg_screen.cpp
index 7e12335..1e90008 100644
--- a/src/screens/mvg_screen.cpp
+++ b/src/screens/mvg_screen.cpp
@@ -1,4 +1,5 @@
 #include "mvg_screen.h"
+#include "../../include/text_utils.h"
 #include <M5Stack.h>
 #include "../../include/theme.h"
 #include "../icons/icons.h"
@@ -59,7 +60,7 @@ void renderMvgScreen(bool forceRefresh) {
         M5.Lcd.print(dep.line);
 
         M5.Lcd.setCursor(60, y + 3);
-        M5.Lcd.print(dep.destination.substring(0, 16));
+        M5.Lcd.print(sanitizeGermanText(dep.destination.substring(0, 16)));
 
         M5.Lcd.setCursor(190, y + 3);
         if (dep.cancelled) {
diff --git a/src/screens/weather_detail_screen.cpp b/src/screens/weather_detail_screen.cpp
index e53213e..922fd15 100644
--- a/src/screens/weather_detail_screen.cpp
+++ b/src/screens/weather_detail_screen.cpp
@@ -1,4 +1,5 @@
 #include "weather_detail_screen.h"
+#include "../../include/text_utils.h"
 #include <M5Stack.h>
 #include "../../include/theme.h"
 #include "../icons/icons.h"
@@ -48,7 +49,7 @@ void renderWeatherDetailScreen(bool forceRefresh) {
         M5.Lcd.printf("%d C", fe.temperature);
 
         M5.Lcd.setCursor(140, y);
-        M5.Lcd.print(fe.description.substring(0, 12));
+        M5.Lcd.print(sanitizeGermanText(fe.description.substring(0, 12)));
 
         if (fe.precipitationType == "rain" && fe.precipitationProbability > 0.0f) {
             M5.Lcd.setTextColor(Theme::ACCENT_RAIN, Theme::BG);