diff --git a/examples/react/functional-component-ts/src/App.tsx b/examples/react/functional-component-ts/src/App.tsx
index 5e49dc95..c69e67cc 100644
--- a/examples/react/functional-component-ts/src/App.tsx
+++ b/examples/react/functional-component-ts/src/App.tsx
@@ -3,6 +3,7 @@ import './App.css';
 import { useAgile, useWatcher } from '@agile-ts/react';
 import { useEvent } from '@agile-ts/event';
 import {
+  COUNTUP,
   MY_COLLECTION,
   MY_COMPUTED,
   MY_EVENT,
@@ -13,6 +14,7 @@ import {
 import { globalBind } from '@agile-ts/core';
 
 let rerenderCount = 0;
+let rerenderCountInCountupView = 0;
 
 const App = (props: any) => {
   // Note: Rerenders twice because of React Strickt Mode (also useState does trigger a rerender twice)
@@ -56,6 +58,19 @@ const App = (props: any) => {
     globalBind('__core__', { ...require('./core') });
   }, []);
 
+  const CountupView = () => {
+    const countup = useAgile(COUNTUP);
+    rerenderCountInCountupView++;
+    return (
+      <div style={{ backgroundColor: 'white', padding: 10 }}>
+        <p style={{ color: 'black' }}>Countup: {countup}</p>
+        <p style={{ color: 'black' }}>
+          Rerender Count of count up View: {rerenderCountInCountupView}
+        </p>
+      </div>
+    );
+  };
+
   return (
     <div className="App">
       <header className="App-header">
@@ -124,7 +139,8 @@ const App = (props: any) => {
           }>
           Update mySelector value
         </button>
-        <p>{rerenderCount}</p>
+        <p>Rerender Count: {rerenderCount}</p>
+        <CountupView />
       </header>
     </div>
   );
diff --git a/examples/react/functional-component-ts/src/core/index.ts b/examples/react/functional-component-ts/src/core/index.ts
index 705736db..28d6caca 100644
--- a/examples/react/functional-component-ts/src/core/index.ts
+++ b/examples/react/functional-component-ts/src/core/index.ts
@@ -30,6 +30,7 @@ App.registerStorage(
   })
 );
 
+export const COUNTUP = App.createState(1).interval((value) => value + 1, 1000);
 export const MY_STATE = App.createState<string>('MyState', { key: 'my-state' }); //.persist();
 export const MY_STATE_2 = App.createState<string>('MyState2', {
   key: 'my-state2',
diff --git a/packages/core/src/state/index.ts b/packages/core/src/state/index.ts
index 6b9cb056..ec8a10e4 100644
--- a/packages/core/src/state/index.ts
+++ b/packages/core/src/state/index.ts
@@ -42,6 +42,8 @@ export class State<ValueType = any> {
 
   public watchers: { [key: string]: StateWatcherCallback<ValueType> } = {};
 
+  public currentInterval?: NodeJS.Timer | number;
+
   /**
    * @public
    * State - Class that holds one Value and causes rerender on subscribed Components
@@ -402,10 +404,12 @@ export class State<ValueType = any> {
       defaultStorageKey: null,
     });
 
-    if (this.persistent)
+    if (this.persistent) {
       Agile.logger.warn(
-        `By persisting the State '${this._key}' twice you overwrite the old Persistent Instance!`
+        `By persisting the State '${this._key}' twice you overwrite the old Persistent Instance!`,
+        this.persistent
       );
+    }
 
     // Create persistent -> Persist Value
     this.persistent = new StatePersistent<ValueType>(this, {
@@ -428,19 +432,63 @@ export class State<ValueType = any> {
    * @param callback - Callback Function
    */
   public onLoad(callback: (success: boolean) => void): this {
-    if (this.persistent) {
-      this.persistent.onLoad = callback;
-
-      // If State is already 'isPersisted' the loading was successful -> callback can be called
-      if (this.isPersisted) callback(true);
-    } else {
+    if (!this.persistent) {
       Agile.logger.error(
         `Please make sure you persist the State '${this._key}' before using the 'onLoad' function!`
       );
+      return this;
     }
+
+    this.persistent.onLoad = callback;
+
+    // If State is already 'isPersisted' the loading was successful -> callback can be called
+    if (this.isPersisted) callback(true);
+
     return this;
   }
 
+  //=========================================================================================================
+  // Interval
+  //=========================================================================================================
+  /**
+   * @public
+   * Calls callback at certain intervals in milliseconds and assigns the callback return value to the State
+   * @param callback- Callback that is called on each interval and should return the new State value
+   * @param ms - The intervals in milliseconds
+   */
+  public interval(
+    callback: (value: ValueType) => ValueType,
+    ms?: number
+  ): this {
+    if (this.currentInterval) {
+      Agile.logger.warn(
+        `You can only have one interval active!`,
+        this.currentInterval
+      );
+      return this;
+    }
+
+    this.currentInterval = setInterval(() => {
+      this.set(callback(this._value));
+    }, ms ?? 1000);
+
+    return this;
+  }
+
+  //=========================================================================================================
+  // Clear Interval
+  //=========================================================================================================
+  /**
+   * @public
+   * Clears the current Interval
+   */
+  public clearInterval(): void {
+    if (this.currentInterval) {
+      clearInterval(this.currentInterval as number);
+      delete this.currentInterval;
+    }
+  }
+
   //=========================================================================================================
   // Copy
   //=========================================================================================================
diff --git a/packages/core/tests/unit/collection/selector.test.ts b/packages/core/tests/unit/collection/selector.test.ts
index 97736f9c..13f18143 100644
--- a/packages/core/tests/unit/collection/selector.test.ts
+++ b/packages/core/tests/unit/collection/selector.test.ts
@@ -18,7 +18,6 @@ describe('Selector Tests', () => {
     dummyCollection = new Collection<ItemInterface>(dummyAgile);
 
     jest.spyOn(Selector.prototype, 'select');
-    console.warn = jest.fn();
   });
 
   it('should create Selector and call initial select (default config)', () => {
diff --git a/packages/core/tests/unit/state/state.test.ts b/packages/core/tests/unit/state/state.test.ts
index 86d89205..7094f34e 100644
--- a/packages/core/tests/unit/state/state.test.ts
+++ b/packages/core/tests/unit/state/state.test.ts
@@ -643,7 +643,8 @@ describe('State Tests', () => {
       });
 
       it('should overwrite existing persistent with a warning', () => {
-        numberState.persistent = new StatePersistent(numberState);
+        const oldPersistent = new StatePersistent(numberState);
+        numberState.persistent = oldPersistent;
 
         numberState.persist('newPersistentKey');
 
@@ -656,7 +657,8 @@ describe('State Tests', () => {
           defaultStorageKey: null,
         });
         expect(console.warn).toHaveBeenCalledWith(
-          `Agile Warn: By persisting the State '${numberState._key}' twice you overwrite the old Persistent Instance!`
+          `Agile Warn: By persisting the State '${numberState._key}' twice you overwrite the old Persistent Instance!`,
+          oldPersistent
         );
       });
     });
@@ -694,6 +696,112 @@ describe('State Tests', () => {
       });
     });
 
+    describe('interval function tests', () => {
+      const dummyCallbackFunction = jest.fn();
+      const dummyCallbackFunction2 = jest.fn();
+
+      beforeEach(() => {
+        jest.useFakeTimers();
+        numberState.set = jest.fn();
+      });
+
+      afterEach(() => {
+        jest.clearAllTimers();
+      });
+
+      it('should create an interval (without custom milliseconds)', () => {
+        dummyCallbackFunction.mockReturnValueOnce(10);
+
+        numberState.interval(dummyCallbackFunction);
+
+        jest.runTimersToTime(1000); // travel 1000s in time -> execute interval
+
+        expect(setInterval).toHaveBeenCalledTimes(1);
+        expect(setInterval).toHaveBeenLastCalledWith(
+          expect.any(Function),
+          1000
+        );
+        expect(dummyCallbackFunction).toHaveBeenCalledWith(numberState._value);
+        expect(numberState.set).toHaveBeenCalledWith(10);
+        expect(numberState.currentInterval).toEqual({
+          id: expect.anything(),
+          ref: expect.anything(),
+          unref: expect.anything(),
+        });
+        expect(console.warn).not.toHaveBeenCalled();
+      });
+
+      it('should create an interval (with custom milliseconds)', () => {
+        dummyCallbackFunction.mockReturnValueOnce(10);
+
+        numberState.interval(dummyCallbackFunction, 2000);
+
+        jest.runTimersToTime(2000); // travel 2000 in time -> execute interval
+
+        expect(setInterval).toHaveBeenCalledTimes(1);
+        expect(setInterval).toHaveBeenLastCalledWith(
+          expect.any(Function),
+          2000
+        );
+        expect(dummyCallbackFunction).toHaveBeenCalledWith(numberState._value);
+        expect(numberState.set).toHaveBeenCalledWith(10);
+        expect(numberState.currentInterval).toEqual({
+          id: expect.anything(),
+          ref: expect.anything(),
+          unref: expect.anything(),
+        });
+        expect(console.warn).not.toHaveBeenCalled();
+      });
+
+      it("shouldn't be able to create second interval and print warning", () => {
+        numberState.interval(dummyCallbackFunction, 3000);
+        const currentInterval = numberState.currentInterval;
+        numberState.interval(dummyCallbackFunction2);
+
+        expect(setInterval).toHaveBeenCalledTimes(1);
+        expect(setInterval).toHaveBeenLastCalledWith(
+          expect.any(Function),
+          3000
+        );
+        expect(numberState.currentInterval).toStrictEqual(currentInterval);
+        expect(console.warn).toHaveBeenCalledWith(
+          'Agile Warn: You can only have one interval active!',
+          numberState.currentInterval
+        );
+      });
+    });
+
+    describe('clearInterval function tests', () => {
+      const dummyCallbackFunction = jest.fn();
+
+      beforeEach(() => {
+        jest.useFakeTimers();
+        numberState.set = jest.fn();
+      });
+
+      afterEach(() => {
+        jest.clearAllTimers();
+      });
+
+      it('should clear existing interval', () => {
+        numberState.interval(dummyCallbackFunction);
+        const currentInterval = numberState.currentInterval;
+
+        numberState.clearInterval();
+
+        expect(clearInterval).toHaveBeenCalledTimes(1);
+        expect(clearInterval).toHaveBeenLastCalledWith(currentInterval);
+        expect(numberState.currentInterval).toBeUndefined();
+      });
+
+      it("shouldn't clear not existing interval", () => {
+        numberState.clearInterval();
+
+        expect(clearInterval).not.toHaveBeenCalled();
+        expect(numberState.currentInterval).toBeUndefined();
+      });
+    });
+
     describe('copy function tests', () => {
       it('should return a reference free copy of the current State Value', () => {
         jest.spyOn(Utils, 'copy');