diff --git a/app/build.gradle b/app/build.gradle
index 946a344..a316797 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -29,6 +29,7 @@ android {
 dependencies {
     implementation 'com.android.support:recyclerview-v7:27.1.1'
     implementation fileTree(include: ['*.jar'], dir: 'libs')
+    implementation 'com.google.firebase:firebase-crash:11.8.0'
     androidTestImplementation('com.android.support.test.espresso:espresso-core:2.2.2', {
         exclude group: 'com.android.support', module: 'support-annotations'
     })
@@ -50,4 +51,7 @@ dependencies {
     // https://github.com/bignerdranch/expandable-recycler-view
     implementation 'com.bignerdranch.android:expandablerecyclerview:3.0.0-RC1'
     implementation files('libs/jericho-html-3.4.jar')
+    implementation 'com.google.firebase:firebase-core:16.0.1'
 }
+
+apply plugin: 'com.google.gms.google-services'
diff --git a/app/google-services.json b/app/google-services.json
new file mode 100644
index 0000000..329a07d
--- /dev/null
+++ b/app/google-services.json
@@ -0,0 +1,55 @@
+{
+  "project_info": {
+    "project_number": "847234418434",
+    "firebase_url": "https://fu-berlin-planner.firebaseio.com",
+    "project_id": "fu-berlin-planner",
+    "storage_bucket": "fu-berlin-planner.appspot.com"
+  },
+  "client": [
+    {
+      "client_info": {
+        "mobilesdk_app_id": "1:847234418434:android:83c6c85cc1bc6041",
+        "android_client_info": {
+          "package_name": "de.sebse.fuplanner"
+        }
+      },
+      "oauth_client": [
+        {
+          "client_id": "847234418434-2qr5e253rmtr9bvln5nn248lobmv95gd.apps.googleusercontent.com",
+          "client_type": 1,
+          "android_info": {
+            "package_name": "de.sebse.fuplanner",
+            "certificate_hash": "8dcea40178f1803c26007711ebe3b1161daa35a3"
+          }
+        },
+        {
+          "client_id": "847234418434-4rbd4t7lghr6ctdskep62jd5b4ed5fmu.apps.googleusercontent.com",
+          "client_type": 3
+        }
+      ],
+      "api_key": [
+        {
+          "current_key": "AIzaSyAE1qDv8AnvGSqIQxh0mT3_f1Qu2cEu3a4"
+        }
+      ],
+      "services": {
+        "analytics_service": {
+          "status": 1
+        },
+        "appinvite_service": {
+          "status": 2,
+          "other_platform_oauth_client": [
+            {
+              "client_id": "847234418434-4rbd4t7lghr6ctdskep62jd5b4ed5fmu.apps.googleusercontent.com",
+              "client_type": 3
+            }
+          ]
+        },
+        "ads_service": {
+          "status": 2
+        }
+      }
+    }
+  ],
+  "configuration_version": "1"
+}
\ No newline at end of file
diff --git a/app/src/main/java/de/sebse/fuplanner/services/Canteen/types/Canteen.java b/app/src/main/java/de/sebse/fuplanner/services/Canteen/types/Canteen.java
index b4dfb4a..075fe39 100644
--- a/app/src/main/java/de/sebse/fuplanner/services/Canteen/types/Canteen.java
+++ b/app/src/main/java/de/sebse/fuplanner/services/Canteen/types/Canteen.java
@@ -79,7 +79,7 @@ public class Canteen implements Serializable, Iterable<Day> {
         int m = calendar.get(Calendar.MONTH)+1;
         int d = calendar.get(Calendar.DAY_OF_MONTH);
 
-        return String.format(Locale.getDefault(), "%d-%d-%d", y, m, d);
+        return String.format(Locale.getDefault(), "%4d-%2d-%2d", y, m, d).replace(' ', '0');
     }
 
     public static Calendar keyToCalendar(String dateString) {
diff --git a/app/src/main/java/de/sebse/fuplanner/tools/SortedListDay.java b/app/src/main/java/de/sebse/fuplanner/tools/SortedListDay.java
index 88a17aa..6576f83 100644
--- a/app/src/main/java/de/sebse/fuplanner/tools/SortedListDay.java
+++ b/app/src/main/java/de/sebse/fuplanner/tools/SortedListDay.java
@@ -8,7 +8,6 @@ import de.sebse.fuplanner.services.Canteen.types.Day;
 public class SortedListDay extends SortedList<Day, Calendar, String> {
     @Override
     int compare(Day o1, Day o2) {
-        // TODO correct implementation
         return Canteen.calendarToKey(o1.getCalendar()).compareTo(Canteen.calendarToKey(o2.getCalendar()));
     }
 
diff --git a/build.gradle b/build.gradle
index be59a9b..9293058 100644
--- a/build.gradle
+++ b/build.gradle
@@ -7,6 +7,7 @@ buildscript {
     }
     dependencies {
         classpath 'com.android.tools.build:gradle:3.1.3'
+        classpath 'com.google.gms:google-services:4.0.0'
 
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files