diff --git a/client/src/app/core/query-params.ts b/client/src/app/core/query-params.ts
new file mode 100644
index 000000000..54c50c0de
--- /dev/null
+++ b/client/src/app/core/query-params.ts
@@ -0,0 +1,30 @@
+
+type QueryParamValue = string | number | boolean;
+
+/**
+ * A key value mapping for params, that should be appended to the url on a new connection.
+ */
+export interface QueryParams {
+    [key: string]: QueryParamValue;
+}
+
+/**
+ * Formats query params for the url.
+ *
+ * @param queryParams
+ * @returns the formatted query params as string
+ */
+export function formatQueryParams(queryParams: QueryParams = {}): string {
+    let params = '';
+    const keys: string[] = Object.keys(queryParams);
+    if (keys.length > 0) {
+        params =
+            '?' +
+            keys
+                .map(key => {
+                    return key + '=' + queryParams[key].toString();
+                })
+                .join('&');
+    }
+    return params;
+}
diff --git a/client/src/app/core/services/app-load.service.ts b/client/src/app/core/services/app-load.service.ts
index c229c66e5..662a6b1ba 100644
--- a/client/src/app/core/services/app-load.service.ts
+++ b/client/src/app/core/services/app-load.service.ts
@@ -11,6 +11,7 @@ import { AssignmentsAppConfig } from '../../site/assignments/assignments.config'
 import { UsersAppConfig } from '../../site/users/users.config';
 import { TagAppConfig } from '../../site/tags/tag.config';
 import { MainMenuService } from './main-menu.service';
+import { HistoryAppConfig } from 'app/site/history/history.config';
 
 /**
  * A list of all app configurations of all delivered apps.
@@ -23,7 +24,8 @@ const appConfigs: AppConfig[] = [
     MotionsAppConfig,
     MediafileAppConfig,
     TagAppConfig,
-    UsersAppConfig
+    UsersAppConfig,
+    HistoryAppConfig
 ];
 
 /**
diff --git a/client/src/app/core/services/data-store.service.ts b/client/src/app/core/services/data-store.service.ts
index 844c76409..bbd2537b7 100644
--- a/client/src/app/core/services/data-store.service.ts
+++ b/client/src/app/core/services/data-store.service.ts
@@ -330,12 +330,25 @@ export class DataStoreService {
     /**
      * Resets the DataStore and set the given models as the new content.
      * @param models A list of models to set the DataStore to.
-     * @param newMaxChangeId Optional. If given, the max change id will be updated.
+     * @param newMaxChangeId Optional. If given, the max change id will be updated
+     * and the store flushed to the storage
      */
-    public async set(models: BaseModel[], newMaxChangeId?: number): Promise<void> {
+    public async set(models?: BaseModel[], newMaxChangeId?: number): Promise<void> {
+        const modelStoreReference = this.modelStore;
         this.modelStore = {};
         this.jsonStore = {};
-        await this.add(models, newMaxChangeId);
+        // Inform about the deletion
+        Object.keys(modelStoreReference).forEach(collectionString => {
+            Object.keys(modelStoreReference[collectionString]).forEach(id => {
+                this.deletedSubject.next({
+                    collection: collectionString,
+                    id: +id
+                });
+            })
+        });
+        if (models && models.length) {
+            await this.add(models, newMaxChangeId);
+        }
     }
 
     /**
diff --git a/client/src/app/core/services/http.service.ts b/client/src/app/core/services/http.service.ts
index 5a549858c..79abaa0f3 100644
--- a/client/src/app/core/services/http.service.ts
+++ b/client/src/app/core/services/http.service.ts
@@ -1,6 +1,8 @@
 import { Injectable } from '@angular/core';
 import { HttpClient, HttpErrorResponse, HttpHeaders } from '@angular/common/http';
 import { TranslateService } from '@ngx-translate/core';
+import { formatQueryParams, QueryParams } from '../query-params';
+import { OpenSlidesStatusService } from './openslides-status.service';
 
 /**
  * Enum for different HTTPMethods
@@ -32,34 +34,45 @@ export class HttpService {
      *
      * @param http The HTTP Client
      * @param translate
+     * @param timeTravel requests are only allowed if history mode is disabled
      */
-    public constructor(private http: HttpClient, private translate: TranslateService) {
-        this.defaultHeaders = new HttpHeaders().set('Content-Type', 'application/json')
+    public constructor(
+        private http: HttpClient,
+        private translate: TranslateService,
+        private OSStatus: OpenSlidesStatusService
+    ) {
+        this.defaultHeaders = new HttpHeaders().set('Content-Type', 'application/json');
     }
 
     /**
-     * Send the a http request the the given URL.
+     * Send the a http request the the given path.
      * Optionally accepts a request body.
      *
-     * @param url the target url, usually starting with /rest
+     * @param path the target path, usually starting with /rest
      * @param method the required HTTP method (i.e get, post, put)
      * @param data optional, if sending a data body is required
+     * @param queryParams optional queryparams to append to the path
      * @param customHeader optional custom HTTP header of required
      * @returns a promise containing a generic
      */
-    private async send<T>(url: string, method: HTTPMethod, data?: any, customHeader?: HttpHeaders): Promise<T> {
-        if (!url.endsWith('/')) {
-            url += '/';
+    private async send<T>(path: string, method: HTTPMethod, data?: any, queryParams?: QueryParams, customHeader?: HttpHeaders): Promise<T> {
+        // end early, if we are in history mode
+        if (this.OSStatus.isInHistoryMode && method !== HTTPMethod.GET) {
+            throw this.handleError('You cannot make changes while in history mode');
         }
 
+        if (!path.endsWith('/')) {
+            path += '/';
+        }
+
+        const url = path + formatQueryParams(queryParams);
         const options = {
             body: data,
             headers: customHeader ? customHeader : this.defaultHeaders
         };
 
         try {
-            const response = await this.http.request<T>(method, url, options).toPromise();
-            return response;
+            return await this.http.request<T>(method, url, options).toPromise();
         } catch (e) {
             throw this.handleError(e);
         }
@@ -73,6 +86,12 @@ export class HttpService {
      */
     private handleError(e: any): string {
         let error = this.translate.instant('Error') + ': ';
+
+        // If the rror is a string already, return it.
+        if (typeof e === 'string') {
+            return error + e;
+        }
+
         // If the error is no HttpErrorResponse, it's not clear what is wrong.
         if (!(e instanceof HttpErrorResponse)) {
             console.error('Unknown error thrown by the http client: ', e);
@@ -119,57 +138,62 @@ export class HttpService {
     }
 
     /**
-     * Exectures a get on a url with a certain object
-     * @param url The url to send the request to.
+     * Executes a get on a path with a certain object
+     * @param path The path to send the request to.
      * @param data An optional payload for the request.
+     * @param queryParams Optional params appended to the path as the query part of the url.
      * @param header optional HTTP header if required
      * @returns A promise holding a generic
      */
-    public async get<T>(url: string, data?: any, header?: HttpHeaders): Promise<T> {
-        return await this.send<T>(url, HTTPMethod.GET, data, header);
+    public async get<T>(path: string, data?: any, queryParams?: QueryParams, header?: HttpHeaders): Promise<T> {
+        return await this.send<T>(path, HTTPMethod.GET, data, queryParams, header);
     }
 
     /**
-     * Exectures a post on a url with a certain object
-     * @param url The url to send the request to.
+     * Executes a post on a path with a certain object
+     * @param path The path to send the request to.
      * @param data An optional payload for the request.
+     * @param queryParams Optional params appended to the path as the query part of the url.
      * @param header optional HTTP header if required
      * @returns A promise holding a generic
      */
-    public async post<T>(url: string, data?: any, header?: HttpHeaders): Promise<T> {
-        return await this.send<T>(url, HTTPMethod.POST, data, header);
+    public async post<T>(path: string, data?: any, queryParams?: QueryParams, header?: HttpHeaders): Promise<T> {
+        return await this.send<T>(path, HTTPMethod.POST, data, queryParams, header);
     }
 
     /**
-     * Exectures a put on a url with a certain object
-     * @param url The url to send the request to.
-     * @param data The payload for the request.
+     * Executes a put on a path with a certain object
+     * @param path The path to send the request to.
+     * @param data An optional payload for the request.
+     * @param queryParams Optional params appended to the path as the query part of the url.
      * @param header optional HTTP header if required
      * @returns A promise holding a generic
      */
-    public async patch<T>(url: string, data: any, header?: HttpHeaders): Promise<T> {
-        return await this.send<T>(url, HTTPMethod.PATCH, data, header);
+    public async patch<T>(path: string, data?: any, queryParams?: QueryParams, header?: HttpHeaders): Promise<T> {
+        return await this.send<T>(path, HTTPMethod.PATCH, data, queryParams, header);
     }
 
     /**
-     * Exectures a put on a url with a certain object
-     * @param url The url to send the request to.
-     * @param data: The payload for the request.
+     * Executes a put on a path with a certain object
+     * @param path The path to send the request to.
+     * @param data An optional payload for the request.
+     * @param queryParams Optional params appended to the path as the query part of the url.
      * @param header optional HTTP header if required
      * @returns A promise holding a generic
      */
-    public async put<T>(url: string, data: any, header?: HttpHeaders): Promise<T> {
-        return await this.send<T>(url, HTTPMethod.PUT, data, header);
+    public async put<T>(path: string, data?: any, queryParams?: QueryParams, header?: HttpHeaders): Promise<T> {
+        return await this.send<T>(path, HTTPMethod.PUT, data, queryParams, header);
     }
 
     /**
      * Makes a delete request.
-     * @param url The url to send the request to.
-     * @param data An optional data to send in the requestbody.
+     * @param url The path to send the request to.
+     * @param data An optional payload for the request.
+     * @param queryParams Optional params appended to the path as the query part of the url.
      * @param header optional HTTP header if required
      * @returns A promise holding a generic
      */
-    public async delete<T>(url: string, data?: any, header?: HttpHeaders): Promise<T> {
-        return await this.send<T>(url, HTTPMethod.DELETE, data, header);
+    public async delete<T>(path: string, data?: any, queryParams?: QueryParams, header?: HttpHeaders): Promise<T> {
+        return await this.send<T>(path, HTTPMethod.DELETE, data, queryParams, header);
     }
 }
diff --git a/client/src/app/core/services/openslides-status.service.spec.ts b/client/src/app/core/services/openslides-status.service.spec.ts
new file mode 100644
index 000000000..aae2d5e9b
--- /dev/null
+++ b/client/src/app/core/services/openslides-status.service.spec.ts
@@ -0,0 +1,17 @@
+import { TestBed, inject } from '@angular/core/testing';
+
+import { E2EImportsModule } from 'e2e-imports.module';
+import { OpenSlidesStatusService } from './openslides-status.service';
+
+describe('OpenSlidesStatusService', () => {
+    beforeEach(() => {
+        TestBed.configureTestingModule({
+            imports: [E2EImportsModule],
+            providers: [OpenSlidesStatusService]
+        });
+    });
+
+    it('should be created', inject([OpenSlidesStatusService], (service: OpenSlidesStatusService) => {
+        expect(service).toBeTruthy();
+    }));
+});
diff --git a/client/src/app/core/services/openslides-status.service.ts b/client/src/app/core/services/openslides-status.service.ts
new file mode 100644
index 000000000..28e1db6cb
--- /dev/null
+++ b/client/src/app/core/services/openslides-status.service.ts
@@ -0,0 +1,42 @@
+import { Injectable } from '@angular/core';
+
+/**
+ * Holds information about OpenSlides. This is not included into other services to
+ * avoid circular dependencies.
+ */
+@Injectable({
+    providedIn: 'root'
+})
+export class OpenSlidesStatusService {
+
+    /**
+     * Saves, if OpenSlides is in the history mode.
+     */
+    private historyMode = false;
+
+    /**
+     * Returns, if OpenSlides is in the history mode.
+     */
+    public get isInHistoryMode(): boolean {
+        return this.historyMode;
+    }
+
+    /**
+     * Ctor, does nothing.
+     */
+    public constructor() {}
+
+    /**
+     * Enters the histroy mode
+     */
+    public enterHistoryMode(): void {
+        this.historyMode = true;
+    }
+
+    /**
+     * Leaves the histroy mode
+     */
+    public leaveHistroyMode(): void {
+       this.historyMode = false;
+    }
+}
diff --git a/client/src/app/core/services/storage.service.ts b/client/src/app/core/services/storage.service.ts
index fc56b1d2d..40fd599bc 100644
--- a/client/src/app/core/services/storage.service.ts
+++ b/client/src/app/core/services/storage.service.ts
@@ -1,5 +1,6 @@
 import { Injectable } from '@angular/core';
 import { LocalStorage } from '@ngx-pwa/local-storage';
+import { OpenSlidesStatusService } from './openslides-status.service';
 
 /**
  * Provides an async API to an key-value store using ngx-pwa which is internally
@@ -13,7 +14,7 @@ export class StorageService {
      * Constructor to create the StorageService. Needs the localStorage service.
      * @param localStorage
      */
-    public constructor(private localStorage: LocalStorage) {}
+    public constructor(private localStorage: LocalStorage, private OSStatus: OpenSlidesStatusService) {}
 
     /**
      * Sets the item into the store asynchronously.
@@ -21,6 +22,7 @@ export class StorageService {
      * @param item
      */
     public async set(key: string, item: any): Promise<void> {
+        this.assertNotHistroyMode();
         if (item === null || item === undefined) {
             await this.remove(key); // You cannot do a setItem with null or undefined...
         } else {
@@ -48,6 +50,7 @@ export class StorageService {
      * @param key The key to remove the value from
      */
     public async remove(key: string): Promise<void> {
+        this.assertNotHistroyMode();
         if (!(await this.localStorage.removeItem(key).toPromise())) {
             throw new Error('Could not delete the item.');
         }
@@ -57,9 +60,18 @@ export class StorageService {
      * Clear the whole cache
      */
     public async clear(): Promise<void> {
-        console.log('clear storage');
+        this.assertNotHistroyMode();
         if (!(await this.localStorage.clear().toPromise())) {
             throw new Error('Could not clear the storage.');
         }
     }
+
+    /**
+     * Throws an error, if we are in history mode.
+     */
+    private assertNotHistroyMode(): void {
+        if (this.OSStatus.isInHistoryMode) {
+            throw new Error('You cannot use the storageService in histroy mode.');
+        }
+    }
 }
diff --git a/client/src/app/core/services/time-travel.service.spec.ts b/client/src/app/core/services/time-travel.service.spec.ts
new file mode 100644
index 000000000..60b32fb50
--- /dev/null
+++ b/client/src/app/core/services/time-travel.service.spec.ts
@@ -0,0 +1,16 @@
+import { TestBed } from '@angular/core/testing';
+
+import { TimeTravelService } from './time-travel.service';
+import { E2EImportsModule } from 'e2e-imports.module';
+
+describe('TimeTravelService', () => {
+    beforeEach(() => TestBed.configureTestingModule({
+        imports: [E2EImportsModule],
+        providers: [TimeTravelService]
+    }));
+
+    it('should be created', () => {
+        const service: TimeTravelService = TestBed.get(TimeTravelService);
+        expect(service).toBeTruthy();
+    });
+});
diff --git a/client/src/app/core/services/time-travel.service.ts b/client/src/app/core/services/time-travel.service.ts
new file mode 100644
index 000000000..dbc37d6e9
--- /dev/null
+++ b/client/src/app/core/services/time-travel.service.ts
@@ -0,0 +1,119 @@
+import { Injectable } from '@angular/core';
+
+import { environment } from 'environments/environment';
+import { CollectionStringModelMapperService } from './collectionStringModelMapper.service';
+import { History } from 'app/shared/models/core/history';
+import { DataStoreService } from './data-store.service';
+import { WebsocketService } from './websocket.service';
+import { BaseModel } from 'app/shared/models/base/base-model';
+import { OpenSlidesStatusService } from './openslides-status.service';
+import { OpenSlidesService } from './openslides.service';
+import { HttpService } from './http.service';
+
+/**
+ * Interface for full history data objects.
+ * The are not too different from the history-objects,
+ * but contain full-data and a timestamp in contrast to a date
+ */
+interface HistoryData {
+    element_id: string;
+    full_data: BaseModel;
+    information: string;
+    timestamp: number;
+    user_id: number;
+}
+
+/**
+ * Service to enable browsing OpenSlides in a previous version.
+ *
+ * This should stop auto updates, save the current ChangeID and overwrite the DataStore with old Values
+ * from the servers History.
+ *
+ * Restoring is nor possible yet. Simply reload
+ */
+@Injectable({
+    providedIn: 'root'
+})
+export class TimeTravelService {
+    /**
+     * Constructs the time travel service
+     *
+     * @param httpService To fetch the history data
+     * @param webSocketService to disable websocket connection
+     * @param modelMapperService to cast history objects into models
+     * @param DS to overwrite the dataStore
+     * @param OSStatus Sets the history status
+     * @param OpenSlides For restarting OpenSlide when exiting the history mode
+     */
+    public constructor(
+        private httpService: HttpService,
+        private webSocketService: WebsocketService,
+        private modelMapperService: CollectionStringModelMapperService,
+        private DS: DataStoreService,
+        private OSStatus: OpenSlidesStatusService,
+        private OpenSlides: OpenSlidesService
+    ) { }
+
+    /**
+     * Main entry point to set OpenSlides to another history point.
+     *
+     * @param history the desired point in the history of OpenSlides
+     */
+    public async loadHistoryPoint(history: History): Promise<void> {
+        await this.stopTime();
+        const fullDataHistory: HistoryData[] = await this.getHistoryData(history);
+        for (const historyObject of fullDataHistory) {
+            let collectionString: string;
+            let id: string;
+            [collectionString, id] = historyObject.element_id.split(':')
+
+            if (historyObject.full_data) {
+                const targetClass = this.modelMapperService.getModelConstructor(collectionString);
+                await this.DS.add([new targetClass(historyObject.full_data)])
+            } else {
+                await this.DS.remove(collectionString, [+id]);
+            }
+        }
+    }
+
+    /**
+     * Leaves the history mode. Just restart OpenSlides:
+     * The active user is chacked, a new WS connection established and
+     * all missed autoupdates are requested.
+     */
+    public async resumeTime(): Promise<void> {
+        await this.DS.set();
+        await this.OpenSlides.reboot();
+        this.OSStatus.leaveHistroyMode();
+    }
+
+    /**
+     * Read the history on a given time
+     *
+     * @param date the Date object
+     * @returns the full history on the given date
+     */
+    private async getHistoryData(history: History): Promise<HistoryData[]> {
+        const historyUrl = '/core/history/'
+        const queryParams = { timestamp: Math.ceil(+history.unixtime) };
+        return this.httpService.get<HistoryData[]>(environment.urlPrefix + historyUrl, null, queryParams);
+    }
+
+    /**
+     * Clears the DataStore and stops the WebSocket connection
+     */
+    private async stopTime(): Promise<void> {
+        this.webSocketService.close();
+        await this.cleanDataStore();
+        this.OSStatus.enterHistoryMode();
+    }
+
+    /**
+     * Clean the DataStore to inject old Data.
+     * Remove everything "but" the history.
+     */
+    private async cleanDataStore(): Promise<void> {
+        const historyArchive = this.DS.getAll(History);
+        await this.DS.set(historyArchive);
+    }
+}
diff --git a/client/src/app/core/services/websocket.service.ts b/client/src/app/core/services/websocket.service.ts
index 624830e81..dcf15f742 100644
--- a/client/src/app/core/services/websocket.service.ts
+++ b/client/src/app/core/services/websocket.service.ts
@@ -2,15 +2,7 @@ import { Injectable, NgZone, EventEmitter } from '@angular/core';
 import { Observable, Subject } from 'rxjs';
 import { MatSnackBar, MatSnackBarRef, SimpleSnackBar } from '@angular/material';
 import { TranslateService } from '@ngx-translate/core';
-
-type QueryParamValue = string | number | boolean;
-
-/**
- * A key value mapping for params, that should be appendet to the url on a new connection.
- */
-interface QueryParams {
-    [key: string]: QueryParamValue;
-}
+import { formatQueryParams, QueryParams } from '../query-params';
 
 /**
  * The generic message format in which messages are send and recieved by the server.
@@ -116,7 +108,7 @@ export class WebsocketService {
         // Create the websocket
         let socketPath = location.protocol === 'https:' ? 'wss://' : 'ws://';
         socketPath += window.location.hostname + ':' + window.location.port + '/ws/';
-        socketPath += this.formatQueryParams(queryParams);
+        socketPath += formatQueryParams(queryParams);
 
         console.log('connect to', socketPath);
         this.websocket = new WebSocket(socketPath);
@@ -225,24 +217,4 @@ export class WebsocketService {
         }
         this.websocket.send(JSON.stringify(message));
     }
-
-    /**
-     * Formats query params for the url.
-     * @param queryParams
-     * @returns the formatted query params as string
-     */
-    private formatQueryParams(queryParams: QueryParams = {}): string {
-        let params = '';
-        const keys: string[] = Object.keys(queryParams);
-        if (keys.length > 0) {
-            params =
-                '?' +
-                keys
-                    .map(key => {
-                        return key + '=' + queryParams[key].toString();
-                    })
-                    .join('&');
-        }
-        return params;
-    }
 }
diff --git a/client/src/app/shared/models/core/history.ts b/client/src/app/shared/models/core/history.ts
new file mode 100644
index 000000000..fc9e49018
--- /dev/null
+++ b/client/src/app/shared/models/core/history.ts
@@ -0,0 +1,39 @@
+
+import { BaseModel } from '../base/base-model';
+
+/**
+ * Representation of a history object.
+ *
+ * @ignore
+ */
+export class History extends BaseModel {
+    public id: number;
+    public element_id: string;
+    public now: string;
+    public information: string;
+    public user_id: number;
+
+    /**
+     * return a date our of the given timestamp
+     *
+     * @returns a Data object
+     */
+    public get date(): Date {
+        return new Date(this.now);
+    }
+
+    /**
+     * Converts the timestamp to unix time
+     */
+    public get unixtime(): number {
+        return Date.parse(this.now) / 1000;
+    }
+
+    public constructor(input?: any) {
+        super('core/history', input);
+    }
+
+    public getTitle(): string {
+        return this.element_id;
+    }
+}
diff --git a/client/src/app/site/assignments/services/assignment-repository.service.spec.ts b/client/src/app/site/assignments/services/assignment-repository.service.spec.ts
index c694cfae7..97f1dcb96 100644
--- a/client/src/app/site/assignments/services/assignment-repository.service.spec.ts
+++ b/client/src/app/site/assignments/services/assignment-repository.service.spec.ts
@@ -1,9 +1,10 @@
 import { TestBed } from '@angular/core/testing';
 
 import { AssignmentRepositoryService } from './assignment-repository.service';
+import { E2EImportsModule } from 'e2e-imports.module';
 
 describe('AssignmentRepositoryService', () => {
-    beforeEach(() => TestBed.configureTestingModule({}));
+    beforeEach(() => TestBed.configureTestingModule({ imports: [E2EImportsModule] }));
 
     it('should be created', () => {
         const service: AssignmentRepositoryService = TestBed.get(AssignmentRepositoryService);
diff --git a/client/src/app/site/assignments/services/assignment-repository.service.ts b/client/src/app/site/assignments/services/assignment-repository.service.ts
index 4d00e5431..c922b410f 100644
--- a/client/src/app/site/assignments/services/assignment-repository.service.ts
+++ b/client/src/app/site/assignments/services/assignment-repository.service.ts
@@ -21,8 +21,13 @@ export class AssignmentRepositoryService extends BaseRepository<ViewAssignment,
     /**
      * Constructor for the Assignment Repository.
      *
+     * @param DS The DataStore
+     * @param mapperService Maps collection strings to classes
      */
-    public constructor(DS: DataStoreService, mapperService: CollectionStringModelMapperService) {
+    public constructor(
+        DS: DataStoreService,
+        mapperService: CollectionStringModelMapperService
+    ) {
         super(DS, mapperService, Assignment, [User, Item, Tag]);
     }
 
diff --git a/client/src/app/site/base/base-repository.ts b/client/src/app/site/base/base-repository.ts
index ba7482be8..65fb11bc3 100644
--- a/client/src/app/site/base/base-repository.ts
+++ b/client/src/app/site/base/base-repository.ts
@@ -1,5 +1,6 @@
-import { OpenSlidesComponent } from '../../openslides.component';
 import { BehaviorSubject, Observable } from 'rxjs';
+
+import { OpenSlidesComponent } from '../../openslides.component';
 import { BaseViewModel } from './base-view-model';
 import { BaseModel, ModelConstructor } from '../../shared/models/base/base-model';
 import { CollectionStringModelMapperService } from '../../core/services/collectionStringModelMapper.service';
@@ -24,7 +25,10 @@ export abstract class BaseRepository<V extends BaseViewModel, M extends BaseMode
     protected readonly viewModelListSubject: BehaviorSubject<V[]> = new BehaviorSubject<V[]>([]);
 
     /**
+     * Construction routine for the base repository
      *
+     * @param DS: The DataStore
+     * @param collectionStringModelMapperService Mapping strings to their corresponding classes
      * @param baseModelCtor The model constructor of which this repository is about.
      * @param depsModelCtors A list of constructors that are used in the view model.
      * If one of those changes, the view models will be updated.
@@ -33,7 +37,7 @@ export abstract class BaseRepository<V extends BaseViewModel, M extends BaseMode
         protected DS: DataStoreService,
         protected collectionStringModelMapperService: CollectionStringModelMapperService,
         protected baseModelCtor: ModelConstructor<M>,
-        protected depsModelCtors?: ModelConstructor<BaseModel>[]
+        protected depsModelCtors?: ModelConstructor<BaseModel>[],
     ) {
         super();
         this.setup();
diff --git a/client/src/app/site/base/base-view.ts b/client/src/app/site/base/base-view.ts
index 526ee53ee..7c17eb5f3 100644
--- a/client/src/app/site/base/base-view.ts
+++ b/client/src/app/site/base/base-view.ts
@@ -1,8 +1,10 @@
-import { BaseComponent } from '../../base.component';
-import { Title } from '@angular/platform-browser';
-import { TranslateService } from '@ngx-translate/core';
-import { MatSnackBar, MatSnackBarRef, SimpleSnackBar } from '@angular/material';
 import { OnDestroy } from '@angular/core';
+import { Title } from '@angular/platform-browser';
+import { MatSnackBar, MatSnackBarRef, SimpleSnackBar } from '@angular/material';
+
+import { TranslateService } from '@ngx-translate/core';
+
+import { BaseComponent } from '../../base.component';
 
 /**
  * A base class for all views. Implements a generic error handling by raising a snack bar
diff --git a/client/src/app/site/config/services/config-repository.service.ts b/client/src/app/site/config/services/config-repository.service.ts
index c7acb7a58..fd0461f6c 100644
--- a/client/src/app/site/config/services/config-repository.service.ts
+++ b/client/src/app/site/config/services/config-repository.service.ts
@@ -86,6 +86,11 @@ export class ConfigRepositoryService extends BaseRepository<ViewConfig, Config>
 
     /**
      * Constructor for ConfigRepositoryService. Requests the constants from the server and creates the config group structure.
+     *
+     * @param DS The DataStore
+     * @param mapperService Maps collection strings to classes
+     * @param dataSend sending changed objects
+     * @param http OpenSlides own HTTP Service
      */
     public constructor(
         DS: DataStoreService,
diff --git a/client/src/app/site/history/components/history-list/history-list.component.html b/client/src/app/site/history/components/history-list/history-list.component.html
new file mode 100644
index 000000000..9d4ccc2b4
--- /dev/null
+++ b/client/src/app/site/history/components/history-list/history-list.component.html
@@ -0,0 +1,58 @@
+<os-head-bar>
+    <!-- Title -->
+    <div class="title-slot">History</div>
+
+    <!-- Menu -->
+    <div class="menu-slot">
+        <button type="button" mat-icon-button [matMenuTriggerFor]="historyMenu"><mat-icon>more_vert</mat-icon></button>
+    </div>
+</os-head-bar>
+
+<mat-table class="os-listview-table on-transition-fade" [dataSource]="dataSource" matSort>
+    <!-- Timestamp -->
+    <ng-container matColumnDef="time">
+        <mat-header-cell *matHeaderCellDef mat-sort-header>Time</mat-header-cell>
+        <mat-cell *matCellDef="let history"> {{ history.getLocaleString('DE-de') }} </mat-cell>
+    </ng-container>
+
+    <!-- Info -->
+    <ng-container matColumnDef="info">
+        <mat-header-cell *matHeaderCellDef mat-sort-header>Info</mat-header-cell>
+        <mat-cell *matCellDef="let history"> {{ history.information }} </mat-cell>
+    </ng-container>
+
+    <!-- Element -->
+    <ng-container matColumnDef="element">
+        <mat-header-cell *matHeaderCellDef mat-sort-header>Element</mat-header-cell>
+
+        <!-- <mat-cell *matCellDef="let history"> {{ history.element_id }} </mat-cell> -->
+        <mat-cell *matCellDef="let history">
+            <div *ngIf="getElementInfo(history)">{{ getElementInfo(history) }}</div>
+            <div
+                class="no-info"
+                matTooltip="{{ 'Select an entry where information at this time was still present' | translate }}"
+                *ngIf="!getElementInfo(history)"
+            >
+                <span>{{ 'No information available' | translate }} ({{ history.element_id }})</span>
+            </div>
+        </mat-cell>
+    </ng-container>
+
+    <!-- User -->
+    <ng-container matColumnDef="user">
+        <mat-header-cell *matHeaderCellDef mat-sort-header>User</mat-header-cell>
+        <mat-cell *matCellDef="let history"> {{ history.user }} </mat-cell>
+    </ng-container>
+
+    <mat-header-row *matHeaderRowDef="getRowDef()"></mat-header-row>
+    <mat-row *matRowDef="let row; columns: getRowDef()" (click)="onClickRow(row)"></mat-row>
+</mat-table>
+
+<mat-paginator class="on-transition-fade" [pageSizeOptions]="[25, 50, 75, 100, 125]"></mat-paginator>
+
+<mat-menu #historyMenu="matMenu">
+    <button mat-menu-item class="red-warning-text" (click)="onDeleteAllButton()">
+        <mat-icon>delete</mat-icon>
+        <span translate>Delete whole history</span>
+    </button>
+</mat-menu>
diff --git a/client/src/app/site/history/components/history-list/history-list.component.scss b/client/src/app/site/history/components/history-list/history-list.component.scss
new file mode 100644
index 000000000..3e36f60e7
--- /dev/null
+++ b/client/src/app/site/history/components/history-list/history-list.component.scss
@@ -0,0 +1,26 @@
+.os-listview-table {
+    /** Time */
+    .mat-column-time {
+        flex: 1 0 50px;
+    }
+
+    /** Element */
+    .mat-column-element {
+        flex: 3 0 50px;
+    }
+
+    /** Info */
+    .mat-column-info {
+        flex: 1 0 50px;
+    }
+
+    /** User */
+    .mat-column-user {
+        flex: 1 0 50px;
+    }
+}
+
+.no-info {
+    font-style: italic;
+    color: slategray; // TODO: Colors per theme
+}
diff --git a/client/src/app/site/history/components/history-list/history-list.component.spec.ts b/client/src/app/site/history/components/history-list/history-list.component.spec.ts
new file mode 100644
index 000000000..edd96bac4
--- /dev/null
+++ b/client/src/app/site/history/components/history-list/history-list.component.spec.ts
@@ -0,0 +1,26 @@
+import { async, ComponentFixture, TestBed } from '@angular/core/testing';
+
+import { E2EImportsModule } from 'e2e-imports.module';
+import { HistoryListComponent } from './history-list.component';
+
+describe('HistoryListComponent', () => {
+    let component: HistoryListComponent;
+    let fixture: ComponentFixture<HistoryListComponent>;
+
+    beforeEach(async(() => {
+        TestBed.configureTestingModule({
+            imports: [E2EImportsModule],
+            declarations: [HistoryListComponent]
+        }).compileComponents();
+    }));
+
+    beforeEach(() => {
+        fixture = TestBed.createComponent(HistoryListComponent);
+        component = fixture.componentInstance;
+        fixture.detectChanges();
+    });
+
+    it('should create', () => {
+        expect(component).toBeTruthy();
+    });
+});
diff --git a/client/src/app/site/history/components/history-list/history-list.component.ts b/client/src/app/site/history/components/history-list/history-list.component.ts
new file mode 100644
index 000000000..5ecd21bba
--- /dev/null
+++ b/client/src/app/site/history/components/history-list/history-list.component.ts
@@ -0,0 +1,112 @@
+import { Component, OnInit } from '@angular/core';
+import { Title } from '@angular/platform-browser';
+import { MatSnackBar } from '@angular/material';
+import { Subject } from 'rxjs';
+
+import { TranslateService } from '@ngx-translate/core';
+
+import { ListViewBaseComponent } from 'app/site/base/list-view-base';
+import { HistoryRepositoryService } from '../../services/history-repository.service';
+import { ViewHistory } from '../../models/view-history';
+
+/**
+ * A list view for the history.
+ *
+ * Should display all changes that have been made in OpenSlides.
+ */
+@Component({
+    selector: 'os-history-list',
+    templateUrl: './history-list.component.html',
+    styleUrls: ['./history-list.component.scss']
+})
+export class HistoryListComponent extends ListViewBaseComponent<ViewHistory> implements OnInit {
+    /**
+     * Subject determine when the custom timestamp subject changes
+     */
+    public customTimestampChanged: Subject<number> = new Subject<number>();
+
+    /**
+     * Constructor for the history list component
+     *
+     * @param titleService Setting the title
+     * @param translate Handle translations
+     * @param matSnackBar Showing errors and messages
+     * @param repo The history repository
+     */
+    public constructor(
+        titleService: Title,
+        translate: TranslateService,
+        matSnackBar: MatSnackBar,
+        private repo: HistoryRepositoryService
+    ) {
+        super(titleService, translate, matSnackBar);
+    }
+
+    /**
+     * Init function for the history list.
+     */
+    public ngOnInit(): void {
+        super.setTitle('History');
+        this.initTable();
+
+        this.repo.getViewModelListObservable().subscribe(history => {
+            this.sortAndPublish(history);
+        });
+    }
+
+    /**
+     * Sorts the given ViewHistory array and sets it in the table data source
+     *
+     * @param unsortedHistoryList
+     */
+    private sortAndPublish(unsortedHistoryList: ViewHistory[]): void {
+        const sortedList = unsortedHistoryList.map(history => history);
+        sortedList.sort((a, b) => b.history.unixtime - a.history.unixtime);
+        this.dataSource.data = sortedList;
+    }
+
+    /**
+     * Returns the row definition for the table
+     *
+     * @returns an array of strings that contains the required row definition
+     */
+    public getRowDef(): string[] {
+        return ['time', 'element', 'info', 'user'];
+    }
+
+    /**
+     * Tries get the title of the BaseModel element corresponding to
+     * a history object.
+     *
+     * @param history the history
+     * @returns the title of an old element or null if it could not be found
+     */
+    public getElementInfo(history: ViewHistory): string {
+        const oldElementTitle = this.repo.getOldModelInfo(history.getCollectionString(), history.getModelID());
+
+        if (oldElementTitle) {
+            return oldElementTitle;
+        } else {
+            return null;
+        }
+    }
+
+    /**
+     * Click handler for rows in the history table.
+     * Serves as an entry point for the time travel routine
+     *
+     * @param history Represents the selected element
+     */
+    public onClickRow(history: ViewHistory): void {
+        this.repo.browseHistory(history).then(() => {
+            this.raiseError(`Temporarily reset OpenSlides to the state from ${history.getLocaleString('DE-de')}`);
+        });
+    }
+
+    /**
+     * Handler for the delete all button
+     */
+    public onDeleteAllButton(): void {
+        this.repo.delete();
+    }
+}
diff --git a/client/src/app/site/history/history-routing.module.ts b/client/src/app/site/history/history-routing.module.ts
new file mode 100644
index 000000000..558dc44d0
--- /dev/null
+++ b/client/src/app/site/history/history-routing.module.ts
@@ -0,0 +1,17 @@
+import { NgModule } from '@angular/core';
+import { Routes, RouterModule } from '@angular/router';
+import { HistoryListComponent } from './components/history-list/history-list.component';
+
+/**
+ * Define the routes for the history module
+ */
+const routes: Routes = [{ path: '', component: HistoryListComponent }];
+
+/**
+ * Define the routing component and setup the routes
+ */
+@NgModule({
+    imports: [RouterModule.forChild(routes)],
+    exports: [RouterModule]
+})
+export class HistoryRoutingModule {}
diff --git a/client/src/app/site/history/history.config.ts b/client/src/app/site/history/history.config.ts
new file mode 100644
index 000000000..657b2afa4
--- /dev/null
+++ b/client/src/app/site/history/history.config.ts
@@ -0,0 +1,20 @@
+import { AppConfig } from '../base/app-config';
+import { History } from 'app/shared/models/core/history';
+
+/**
+ * Config object for history.
+ * Hooks into the navigation.
+ */
+export const HistoryAppConfig: AppConfig = {
+    name: 'history',
+    models: [{ collectionString: 'core/history', model: History }],
+    mainMenuEntries: [
+        {
+            route: '/history',
+            displayName: 'History',
+            icon: 'history',
+            weight: 1200,
+            permission: 'core.view_history'
+        }
+    ]
+};
diff --git a/client/src/app/site/history/history.module.ts b/client/src/app/site/history/history.module.ts
new file mode 100644
index 000000000..a8a2084a9
--- /dev/null
+++ b/client/src/app/site/history/history.module.ts
@@ -0,0 +1,16 @@
+import { NgModule } from '@angular/core';
+import { CommonModule } from '@angular/common';
+
+import { HistoryRoutingModule } from './history-routing.module';
+import { SharedModule } from '../../shared/shared.module';
+import { HistoryListComponent } from './components/history-list/history-list.component';
+
+/**
+ * App module for the history feature.
+ * Declares the used components.
+ */
+@NgModule({
+    imports: [CommonModule, HistoryRoutingModule, SharedModule],
+    declarations: [HistoryListComponent]
+})
+export class HistoryModule {}
diff --git a/client/src/app/site/history/models/view-history.ts b/client/src/app/site/history/models/view-history.ts
new file mode 100644
index 000000000..1018497fe
--- /dev/null
+++ b/client/src/app/site/history/models/view-history.ts
@@ -0,0 +1,132 @@
+import { BaseViewModel } from 'app/site/base/base-view-model';
+import { History } from 'app/shared/models/core/history';
+import { User } from 'app/shared/models/users/user';
+import { BaseModel } from 'app/shared/models/base/base-model';
+
+/**
+ * View model for history objects
+ */
+export class ViewHistory extends BaseViewModel {
+    /**
+     * Private BaseModel of the history
+     */
+    private _history: History;
+
+    /**
+     * Real representation of the user who altered the history.
+     * Determined from `History.user_id`
+     */
+    private _user: User;
+
+    /**
+     * Read the history property
+     */
+    public get history(): History {
+        return this._history ? this._history : null;
+    }
+
+    /**
+     * Read the user property
+     */
+    public get user(): User {
+        return this._user ? this._user : null;
+    }
+
+    /**
+     * Get the ID of the history object
+     * Required by BaseViewModel
+     *
+     * @returns the ID as number
+     */
+    public get id(): number {
+        return this.history ? this.history.id : null;
+    }
+
+    /**
+     * Get the elementIs of the history object
+     *
+     * @returns the element ID as String
+     */
+    public get element_id(): string {
+        return this.history ? this.history.element_id : null;
+    }
+
+    /**
+     * Get the information about the history
+     *
+     * @returns a string with the information to the history object
+     */
+    public get information(): string {
+        return this.history ? this.history.information : null;
+    }
+
+    /**
+     * Get the time of the history as number
+     *
+     * @returns the unix timestamp as number
+     */
+    public get now(): string {
+        return this.history ? this.history.now : null;
+    }
+
+    /**
+     * Construction of a ViewHistory
+     *
+     * @param history the real history BaseModel
+     * @param user the real user BaseModel
+     */
+    public constructor(history?: History, user?: User) {
+        super();
+        this._history = history;
+        this._user = user;
+    }
+
+    /**
+     * Converts the date (this.now) to a time and date string.
+     *
+     * @param locale locale indicator, i.e 'de-DE'
+     * @returns a human readable kind of time and date representation
+     */
+    public getLocaleString(locale: string): string {
+        return this.history.date ? this.history.date.toLocaleString(locale) : null;
+    }
+
+    /**
+     * Converts elementID into collection string
+     * @returns the CollectionString to the model
+     */
+    public getCollectionString(): string {
+        return this.element_id.split(":")[0]
+    }
+
+    /**
+     * Extract the models ID from the elementID
+     * @returns a model id
+     */
+    public getModelID(): number {
+        return +this.element_id.split(":")[1]
+    }
+
+    /**
+     * Get the history objects title
+     * Required by BaseViewModel
+     *
+     * @returns history.getTitle which returns the element_id
+     */
+    public getTitle(): string {
+        return this.history.getTitle();
+    }
+
+    /**
+     * Updates the history object with new values
+     *
+     * @param update potentially the new values for history or it's components.
+     */
+    public updateValues(update: BaseModel): void {
+        if (update instanceof History && this.history.id === update.id) {
+            this._history = update;
+        } else if (this.history && update instanceof User && this.history.user_id === update.id) {
+            this._user = update;
+        }
+    }
+}
diff --git a/client/src/app/site/history/services/history-repository.service.spec.ts b/client/src/app/site/history/services/history-repository.service.spec.ts
new file mode 100644
index 000000000..fc8a86317
--- /dev/null
+++ b/client/src/app/site/history/services/history-repository.service.spec.ts
@@ -0,0 +1,18 @@
+import { TestBed } from '@angular/core/testing';
+
+import { HistoryRepositoryService } from './history-repository.service';
+import { E2EImportsModule } from 'e2e-imports.module';
+
+describe('HistoryRepositoryService', () => {
+    beforeEach(() => {
+        TestBed.configureTestingModule({
+            imports: [E2EImportsModule],
+            providers: [HistoryRepositoryService]
+        });
+    });
+
+    it('should be created', () => {
+        const service = TestBed.get(HistoryRepositoryService);
+        expect(service).toBeTruthy();
+    });
+});
diff --git a/client/src/app/site/history/services/history-repository.service.ts b/client/src/app/site/history/services/history-repository.service.ts
new file mode 100644
index 000000000..36796e7ce
--- /dev/null
+++ b/client/src/app/site/history/services/history-repository.service.ts
@@ -0,0 +1,102 @@
+import { Injectable } from '@angular/core';
+
+import { CollectionStringModelMapperService } from 'app/core/services/collectionStringModelMapper.service';
+import { DataStoreService } from 'app/core/services/data-store.service';
+import { BaseRepository } from 'app/site/base/base-repository';
+import { History } from 'app/shared/models/core/history';
+import { User } from 'app/shared/models/users/user';
+import { Identifiable } from 'app/shared/models/base/identifiable';
+import { HttpService } from 'app/core/services/http.service';
+import { ViewHistory } from '../models/view-history';
+import { TimeTravelService } from 'app/core/services/time-travel.service';
+import { BaseModel } from 'app/shared/models/base/base-model';
+
+/**
+ * Repository for the history.
+ *
+ * Gets new history objects/entries and provides them for the view.
+ */
+@Injectable({
+    providedIn: 'root'
+})
+export class HistoryRepositoryService extends BaseRepository<ViewHistory, History> {
+    /**
+     * Constructs the history repository
+     *
+     * @param DS The DataStore
+     * @param mapperService mapps the models to the collection string
+     * @param httpService OpenSlides own HTTP service
+     * @param timeTravel To change the time
+     */
+    public constructor(
+        DS: DataStoreService,
+        mapperService: CollectionStringModelMapperService,
+        private httpService: HttpService,
+        private timeTravel: TimeTravelService
+    ) {
+        super(DS, mapperService, History, [User]);
+    }
+
+    /**
+     * Clients usually do not need to create a history object themselves
+     * @ignore
+     */
+    public async create(): Promise<Identifiable> {
+        throw new Error('You cannot create a history object');
+    }
+
+    /**
+     * Clients usually do not need to modify existing history objects
+     * @ignore
+     */
+    public async update(): Promise<void> {
+        throw new Error('You cannot update a history object');
+    }
+
+    /**
+     * Sends a post-request to delete history objects
+     */
+    public async delete(): Promise<void> {
+        const restPath = 'rest/core/history/clear_history/';
+        await this.httpService.post(restPath);
+    }
+
+    /**
+     * Get the ListTitle of a history Element from the dataStore
+     * using the collection string and the ID.
+     *
+     * @param collectionString the models collection string
+     * @param id the models id
+     * @returns the ListTitle or null if the model was deleted already
+     */
+    public getOldModelInfo(collectionString: string, id: number): string {
+        const oldModel: BaseModel = this.DS.get(collectionString, id);
+        if (oldModel) {
+            return oldModel.getListTitle();
+        } else {
+            return null;
+        }
+    }
+
+    /**
+     * Creates a new ViewHistory objects out of a historyObject
+     *
+     * @param history the source history object
+     * @return a new ViewHistory object
+     */
+    public createViewModel(history: History): ViewHistory {
+        const user = this.DS.get(User, history.user_id);
+        return new ViewHistory(history, user);
+    }
+
+    /**
+     * Get the full data on the given date and use the
+     * TimeTravelService to browse the history on the
+     * given date
+     *
+     * @param viewHistory determines to point to travel back to
+     */
+    public async browseHistory(viewHistory: ViewHistory): Promise<void> {
+        return this.timeTravel.loadHistoryPoint(viewHistory.history);
+    }
+}
diff --git a/client/src/app/site/mediafiles/services/mediafile-repository.service.ts b/client/src/app/site/mediafiles/services/mediafile-repository.service.ts
index a8c0b56e7..0b6e63d91 100644
--- a/client/src/app/site/mediafiles/services/mediafile-repository.service.ts
+++ b/client/src/app/site/mediafiles/services/mediafile-repository.service.ts
@@ -78,7 +78,7 @@ export class MediafileRepositoryService extends BaseRepository<ViewMediafile, Me
     public async uploadFile(file: FormData): Promise<Identifiable> {
         const restPath = `rest/mediafiles/mediafile/`;
         const emptyHeader = new HttpHeaders();
-        return this.httpService.post<Identifiable>(restPath, file, emptyHeader);
+        return this.httpService.post<Identifiable>(restPath, file, {}, emptyHeader);
     }
 
     /**
diff --git a/client/src/app/site/motions/services/category-repository.service.ts b/client/src/app/site/motions/services/category-repository.service.ts
index ec966d5ea..976d0650b 100644
--- a/client/src/app/site/motions/services/category-repository.service.ts
+++ b/client/src/app/site/motions/services/category-repository.service.ts
@@ -27,9 +27,11 @@ export class CategoryRepositoryService extends BaseRepository<ViewCategory, Cate
      * Creates a CategoryRepository
      * Converts existing and incoming category to ViewCategories
      * Handles CRUD using an observer to the DataStore
-     * @param DS
-     * @param dataSend
-     * @param httpService
+     *
+     * @param DS The DataStore
+     * @param mapperService Maps collection strings to classes
+     * @param dataSend sending changed objects
+     * @param httpService OpenSlides own HTTP service
      */
     public constructor(
         protected DS: DataStoreService,
diff --git a/client/src/app/site/motions/services/change-recommendation-repository.service.ts b/client/src/app/site/motions/services/change-recommendation-repository.service.ts
index e1053487c..f824aa8c0 100644
--- a/client/src/app/site/motions/services/change-recommendation-repository.service.ts
+++ b/client/src/app/site/motions/services/change-recommendation-repository.service.ts
@@ -32,8 +32,10 @@ export class ChangeRecommendationRepositoryService extends BaseRepository<ViewCh
      *
      * Converts existing and incoming motions to ViewMotions
      * Handles CRUD using an observer to the DataStore
-     * @param DS
-     * @param dataSend
+     *
+     * @param DS The DataStore
+     * @param mapperService Maps collection strings to classes
+     * @param dataSend sending changed objects
      */
     public constructor(
         DS: DataStoreService,
diff --git a/client/src/app/site/motions/services/local-permissions.service.ts b/client/src/app/site/motions/services/local-permissions.service.ts
index db87c5ae7..ec3ee9b9d 100644
--- a/client/src/app/site/motions/services/local-permissions.service.ts
+++ b/client/src/app/site/motions/services/local-permissions.service.ts
@@ -16,11 +16,7 @@ export class LocalPermissionsService {
         private configService: ConfigService,
     ) {
         // load config variables
-        this.configService.get('motions_min_supporters').subscribe(
-            (supporters: number): void => {
-                this.configMinSupporters = supporters;
-            }
-        );
+        this.configService.get('motions_min_supporters').subscribe(supporters => (this.configMinSupporters = supporters));
     }
 
     /**
diff --git a/client/src/app/site/motions/services/motion-repository.service.ts b/client/src/app/site/motions/services/motion-repository.service.ts
index 15bd26d1a..721763431 100644
--- a/client/src/app/site/motions/services/motion-repository.service.ts
+++ b/client/src/app/site/motions/services/motion-repository.service.ts
@@ -40,15 +40,19 @@ import { ViewMotionAmendedParagraph } from '../models/view-motion-amended-paragr
     providedIn: 'root'
 })
 export class MotionRepositoryService extends BaseRepository<ViewMotion, Motion> {
+
     /**
      * Creates a MotionRepository
      *
      * Converts existing and incoming motions to ViewMotions
      * Handles CRUD using an observer to the DataStore
-     * @param {DataStoreService} DS
-     * @param {DataSendService} dataSend
-     * @param {LinenumberingService} lineNumbering
-     * @param {DiffService} diff
+     *
+     * @param DS The DataStore
+     * @param mapperService Maps collection strings to classes
+     * @param dataSend sending changed objects
+     * @param httpService OpenSlides own Http service
+     * @param lineNumbering Line numbering for motion text
+     * @param diff Display changes in motion text as diff.
      */
     public constructor(
         DS: DataStoreService,
diff --git a/client/src/app/site/motions/services/statute-paragraph-repository.service.ts b/client/src/app/site/motions/services/statute-paragraph-repository.service.ts
index c3625c79f..b010f2442 100644
--- a/client/src/app/site/motions/services/statute-paragraph-repository.service.ts
+++ b/client/src/app/site/motions/services/statute-paragraph-repository.service.ts
@@ -22,7 +22,10 @@ export class StatuteParagraphRepositoryService extends BaseRepository<ViewStatut
      * Creates a StatuteParagraphRepository
      * Converts existing and incoming statute paragraphs to ViewStatuteParagraphs
      * Handles CRUD using an observer to the DataStore
-     * @param DataSend
+     *
+     * @param DS The DataStore
+     * @param mapperService Maps collection strings to classes
+     * @param dataSend sending changed objects
      */
     public constructor(
         DS: DataStoreService,
diff --git a/client/src/app/site/site-routing.module.ts b/client/src/app/site/site-routing.module.ts
index 4c9487b9c..9575dd338 100644
--- a/client/src/app/site/site-routing.module.ts
+++ b/client/src/app/site/site-routing.module.ts
@@ -46,6 +46,10 @@ const routes: Routes = [
             {
                 path: 'tags',
                 loadChildren: './tags/tag.module#TagModule'
+            },
+            {
+                path: 'history',
+                loadChildren: './history/history.module#HistoryModule'
             }
         ],
         canActivateChild: [AuthGuard]
diff --git a/client/src/app/site/site.component.html b/client/src/app/site/site.component.html
index cef298e29..53a2e6072 100644
--- a/client/src/app/site/site.component.html
+++ b/client/src/app/site/site.component.html
@@ -1,3 +1,7 @@
+<div class="history-mode-indicator" *ngIf="OSStatus.isInHistoryMode">
+    <span translate>You are using the history mode of OpenSlides. Changes will not be saved.</span>
+    <a (click)="timeTravel.resumeTime()" translate>Exit</a>
+</div>
 <mat-sidenav-container #siteContainer class='main-container' (backdropClick)="toggleSideNav()">
     <mat-sidenav #sideNav [mode]="vp.isMobile ? 'push' : 'side'" [opened]='!vp.isMobile' disableClose='!vp.isMobile'
         class="side-panel">
diff --git a/client/src/app/site/site.component.scss b/client/src/app/site/site.component.scss
index 248309967..fe739fe2e 100644
--- a/client/src/app/site/site.component.scss
+++ b/client/src/app/site/site.component.scss
@@ -15,8 +15,7 @@
 }
 .os-logo-container:focus,
 .os-logo-container:active,
-.os-logo-container:hover,
- {
+.os-logo-container:hover {
     border: none;
     outline: none;
 }
@@ -42,6 +41,31 @@ mat-sidenav-container {
     padding-bottom: 70px;
 }
 
+.history-mode-indicator {
+    position: fixed;
+    width: 100%;
+    z-index: 10;
+    background: repeating-linear-gradient(45deg, #ffee00, #ffee00 10px, #070600 10px, #000000 20px);
+    text-align: center;
+    line-height: 20px;
+    height: 20px;
+
+    span {
+        padding: 2px;
+        color: #000000;
+        background: #ffee00;
+    }
+
+    a {
+        padding: 2px;
+        cursor: pointer;
+        font-weight: bold;
+        text-decoration: none;
+        background: #ffee00;
+        color: #000000;
+    }
+}
+
 main {
     display: flex;
     flex-direction: column;
diff --git a/client/src/app/site/site.component.ts b/client/src/app/site/site.component.ts
index 81b7e1102..d6f5d584b 100644
--- a/client/src/app/site/site.component.ts
+++ b/client/src/app/site/site.component.ts
@@ -10,6 +10,8 @@ import { pageTransition, navItemAnim } from 'app/shared/animations';
 import { MatDialog, MatSidenav } from '@angular/material';
 import { ViewportService } from '../core/services/viewport.service';
 import { MainMenuService } from '../core/services/main-menu.service';
+import { OpenSlidesStatusService } from 'app/core/services/openslides-status.service';
+import { TimeTravelService } from 'app/core/services/time-travel.service';
 
 @Component({
     selector: 'os-site',
@@ -48,11 +50,14 @@ export class SiteComponent extends BaseComponent implements OnInit {
      * Constructor
      *
      * @param authService
-     * @param router
+     * @param route
      * @param operator
      * @param vp
      * @param translate
      * @param dialog
+     * @param mainMenuService
+     * @param OSStatus
+     * @param timeTravel
      */
     public constructor(
         private authService: AuthService,
@@ -61,7 +66,9 @@ export class SiteComponent extends BaseComponent implements OnInit {
         public vp: ViewportService,
         public translate: TranslateService,
         public dialog: MatDialog,
-        public mainMenuService: MainMenuService // used in the component
+        public mainMenuService: MainMenuService,
+        public OSStatus: OpenSlidesStatusService,
+        public timeTravel: TimeTravelService
     ) {
         super();
 
diff --git a/client/src/app/site/tags/services/tag-repository.service.ts b/client/src/app/site/tags/services/tag-repository.service.ts
index 902574335..2b1dbc635 100644
--- a/client/src/app/site/tags/services/tag-repository.service.ts
+++ b/client/src/app/site/tags/services/tag-repository.service.ts
@@ -25,7 +25,10 @@ export class TagRepositoryService extends BaseRepository<ViewTag, Tag> {
      * Creates a TagRepository
      * Converts existing and incoming Tags to ViewTags
      * Handles CRUD using an observer to the DataStore
-     * @param DataSend
+     *
+     * @param DS DataStore
+     * @param mapperService Maps collection strings to classes
+     * @param dataSend sending changed objects
      */
     public constructor(
         protected DS: DataStoreService,
diff --git a/client/src/app/site/users/services/group-repository.service.ts b/client/src/app/site/users/services/group-repository.service.ts
index 9ea9b17a8..7a591005c 100644
--- a/client/src/app/site/users/services/group-repository.service.ts
+++ b/client/src/app/site/users/services/group-repository.service.ts
@@ -33,8 +33,10 @@ export class GroupRepositoryService extends BaseRepository<ViewGroup, Group> {
 
     /**
      * Constructor calls the parent constructor
-     * @param DS Store
-     * @param dataSend Sending Data
+     * @param DS The DataStore
+     * @param mapperService Maps collection strings to classes
+     * @param dataSend sending changed objects
+     * @param constants reading out the OpenSlides constants
      */
     public constructor(
         DS: DataStoreService,
diff --git a/client/src/app/site/users/services/user-repository.service.ts b/client/src/app/site/users/services/user-repository.service.ts
index 33acc7ec6..bed081c51 100644
--- a/client/src/app/site/users/services/user-repository.service.ts
+++ b/client/src/app/site/users/services/user-repository.service.ts
@@ -19,7 +19,11 @@ import { CollectionStringModelMapperService } from '../../../core/services/colle
 })
 export class UserRepositoryService extends BaseRepository<ViewUser, User> {
     /**
-     * Constructor calls the parent constructor
+     * Constructor for the user repo
+     *
+     * @param DS The DataStore
+     * @param mapperService Maps collection strings to classes
+     * @param dataSend sending changed objects
      */
     public constructor(
         DS: DataStoreService,
diff --git a/openslides/motions/signals.py b/openslides/motions/signals.py
index cb4911519..ffaefacd1 100644
--- a/openslides/motions/signals.py
+++ b/openslides/motions/signals.py
@@ -26,7 +26,7 @@ def create_builtin_workflows(sender, **kwargs):
                       workflow=workflow_1,
                       action_word='Accept',
                       recommendation_label='Acceptance',
-                      css_class='success'),
+                      css_class='success',
                       merge_amendment_into_final=True)
     state_1_2.save(skip_autoupdate=True)
     state_1_3 = State(name=ugettext_noop('rejected'),
@@ -64,7 +64,7 @@ def create_builtin_workflows(sender, **kwargs):
                       workflow=workflow_2,
                       action_word='Accept',
                       recommendation_label='Acceptance',
-                      css_class='success'),
+                      css_class='success',
                       merge_amendment_into_final=True)
     state_2_3.save(skip_autoupdate=True)
     state_2_4 = State(name=ugettext_noop('rejected'),