diff --git a/database/src/main/java/info/metadude/android/eventfahrplan/database/sqliteopenhelper/AlarmsDBOpenHelper.java b/database/src/main/java/info/metadude/android/eventfahrplan/database/sqliteopenhelper/AlarmsDBOpenHelper.java
index 4915eaa4d6..451cf0a105 100644
--- a/database/src/main/java/info/metadude/android/eventfahrplan/database/sqliteopenhelper/AlarmsDBOpenHelper.java
+++ b/database/src/main/java/info/metadude/android/eventfahrplan/database/sqliteopenhelper/AlarmsDBOpenHelper.java
@@ -10,7 +10,7 @@
 
 public class AlarmsDBOpenHelper extends SQLiteOpenHelper {
 
-    private static final int DATABASE_VERSION = 6;
+    private static final int DATABASE_VERSION = 5;
 
     private static final String DATABASE_NAME = "alarms";
 
@@ -53,12 +53,7 @@ public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
             onCreate(db);
         }
         if (oldVersion < 5) {
-            // Clear database from rC3 12/2020.
-            db.execSQL("DROP TABLE IF EXISTS " + AlarmsTable.NAME);
-            onCreate(db);
-        }
-        if (oldVersion < 6) {
-            // Clear database from rC3 NOWHERE 12/2021 & 36C3 2019.
+            // Clear database from rC3 12/2020 & KotlinConf 2023.
             db.execSQL("DROP TABLE IF EXISTS " + AlarmsTable.NAME);
             onCreate(db);
         }
diff --git a/database/src/main/java/info/metadude/android/eventfahrplan/database/sqliteopenhelper/HighlightDBOpenHelper.java b/database/src/main/java/info/metadude/android/eventfahrplan/database/sqliteopenhelper/HighlightDBOpenHelper.java
index 3a40abb3a9..22bb9557cd 100644
--- a/database/src/main/java/info/metadude/android/eventfahrplan/database/sqliteopenhelper/HighlightDBOpenHelper.java
+++ b/database/src/main/java/info/metadude/android/eventfahrplan/database/sqliteopenhelper/HighlightDBOpenHelper.java
@@ -11,7 +11,7 @@
 
 public class HighlightDBOpenHelper extends SQLiteOpenHelper {
 
-    private static final int DATABASE_VERSION = 5;
+    private static final int DATABASE_VERSION = 4;
 
     private static final String DATABASE_NAME = "highlight";
 
diff --git a/database/src/main/java/info/metadude/android/eventfahrplan/database/sqliteopenhelper/MetaDBOpenHelper.java b/database/src/main/java/info/metadude/android/eventfahrplan/database/sqliteopenhelper/MetaDBOpenHelper.java
index bbc1d5581f..bb14be9ded 100644
--- a/database/src/main/java/info/metadude/android/eventfahrplan/database/sqliteopenhelper/MetaDBOpenHelper.java
+++ b/database/src/main/java/info/metadude/android/eventfahrplan/database/sqliteopenhelper/MetaDBOpenHelper.java
@@ -13,7 +13,7 @@
 
 public class MetaDBOpenHelper extends SQLiteOpenHelper {
 
-    private static final int DATABASE_VERSION = 9;
+    private static final int DATABASE_VERSION = 6;
 
     private static final String DATABASE_NAME = "meta";
 
@@ -42,10 +42,6 @@ public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
             db.execSQL("ALTER TABLE " + MetasTable.NAME + " ADD COLUMN " +
                     Columns.ETAG + " TEXT DEFAULT " + Defaults.ETAG_DEFAULT);
         }
-        if (oldVersion < 6 && newVersion >= 6) {
-            db.execSQL("ALTER TABLE " + MetasTable.NAME + " ADD COLUMN " +
-                    Columns.TIME_ZONE_NAME + " TEXT");
-        }
         if (oldVersion < 4) {
             // Clear database from 34C3.
             db.execSQL("DROP TABLE IF EXISTS " + MetasTable.NAME);
@@ -56,22 +52,10 @@ public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
             db.execSQL("DROP TABLE IF EXISTS " + MetasTable.NAME);
             onCreate(db);
         }
-        if (oldVersion < 7) {
-            // Clear database from rC3 12/2020.
-            db.execSQL("DROP TABLE IF EXISTS " + MetasTable.NAME);
-            onCreate(db);
-        }
-        if (oldVersion < 8) {
-            // Clear database from rC3 NOWHERE 12/2021 & 36C3 2019.
+        if (oldVersion < 6) {
+            // Clear database from KotlinConf 2023.
             db.execSQL("DROP TABLE IF EXISTS " + MetasTable.NAME);
             onCreate(db);
         }
-        if (oldVersion < 9) {
-            boolean columnExists = SQLiteDatabaseExtensions.columnExists(db, MetasTable.NAME, Columns.SCHEDULE_LAST_MODIFIED);
-            if (!columnExists) {
-                db.execSQL("ALTER TABLE " + MetasTable.NAME + " ADD COLUMN " +
-                        Columns.SCHEDULE_LAST_MODIFIED + " TEXT DEFAULT ''");
-            }
-        }
     }
 }
diff --git a/database/src/main/java/info/metadude/android/eventfahrplan/database/sqliteopenhelper/SessionsDBOpenHelper.java b/database/src/main/java/info/metadude/android/eventfahrplan/database/sqliteopenhelper/SessionsDBOpenHelper.java
index 5e76eedf67..9fd56eaa3a 100644
--- a/database/src/main/java/info/metadude/android/eventfahrplan/database/sqliteopenhelper/SessionsDBOpenHelper.java
+++ b/database/src/main/java/info/metadude/android/eventfahrplan/database/sqliteopenhelper/SessionsDBOpenHelper.java
@@ -16,7 +16,7 @@
 
 public class SessionsDBOpenHelper extends SQLiteOpenHelper {
 
-    private static final int DATABASE_VERSION = 15;
+    private static final int DATABASE_VERSION = 10;
 
     private static final String DATABASE_NAME = "lectures"; // Keep table name to avoid database migration.
 
@@ -131,40 +131,11 @@ public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
             db.execSQL("DROP TABLE IF EXISTS " + SessionsTable.NAME);
             onCreate(db);
         }
-        if (oldVersion < 10 && newVersion >= 10) {
-            db.execSQL(SESSION_BY_NOTIFICATION_ID_TABLE_CREATE);
-        }
-        if (oldVersion < 11 && newVersion >= 11) {
-            boolean columnExists = SQLiteDatabaseExtensions.columnExists(db, SessionsTable.NAME, Columns.TIME_ZONE_OFFSET);
-            if (!columnExists) {
-                db.execSQL("ALTER TABLE " + SessionsTable.NAME + " ADD COLUMN " + Columns.TIME_ZONE_OFFSET + " INTEGER DEFAULT NULL");
-            }
-        }
-        if (oldVersion < 12) {
-            // Clear database from rC3 12/2020.
-            db.execSQL("DROP TABLE IF EXISTS " + SessionsTable.NAME);
-            db.execSQL("DROP TABLE IF EXISTS " + SessionByNotificationIdTable.NAME);
-            onCreate(db);
-        }
-        if (oldVersion < 13) {
-            // Clear database from rC3 NOWHERE 12/2021 & 36C3 2019.
+        if (oldVersion < 10) {
+            // Clear database from KotlinConf 2023.
             db.execSQL("DROP TABLE IF EXISTS " + SessionsTable.NAME);
-            db.execSQL("DROP TABLE IF EXISTS " + SessionByNotificationIdTable.NAME);
             onCreate(db);
         }
-        if (oldVersion < 14) {
-            boolean columnExists = SQLiteDatabaseExtensions.columnExists(db, SessionsTable.NAME, Columns.ROOM_IDENTIFIER);
-            if (!columnExists) {
-                db.execSQL("ALTER TABLE " + SessionsTable.NAME + " ADD COLUMN " + Columns.ROOM_IDENTIFIER + " TEXT DEFAULT ''");
-            }
-        }
-        if (oldVersion < 15) {
-            boolean columnExists = SQLiteDatabaseExtensions.columnExists(db, SessionsTable.NAME, Columns.FEEDBACK_URL);
-            if (!columnExists) {
-                db.execSQL("ALTER TABLE " + SessionsTable.NAME + " ADD COLUMN " + Columns.FEEDBACK_URL + " TEXT DEFAULT NULL");
-            }
-        }
-
 
     }
 }