diff --git a/dist/tween.amd.js b/dist/tween.amd.js
index 8d82ed6e..ee33f1dd 100644
--- a/dist/tween.amd.js
+++ b/dist/tween.amd.js
@@ -215,7 +215,13 @@ define(['exports'], (function (exports) { 'use strict';
         },
     });
 
-    var now = function () { return performance.now(); };
+    var _nowFunc = function () { return performance.now(); };
+    var now = function () {
+        return _nowFunc();
+    };
+    function setNow(nowFunction) {
+        _nowFunc = nowFunction;
+    }
 
     /**
      * Controlling groups of tweens
@@ -1139,6 +1145,7 @@ define(['exports'], (function (exports) { 'use strict';
         Group: Group,
         Interpolation: Interpolation,
         now: now,
+        setNow: setNow,
         Sequence: Sequence,
         nextId: nextId,
         Tween: Tween,
@@ -1398,6 +1405,7 @@ define(['exports'], (function (exports) { 'use strict';
     exports.now = now;
     exports.remove = remove;
     exports.removeAll = removeAll;
+    exports.setNow = setNow;
     exports.update = update;
 
     Object.defineProperty(exports, '__esModule', { value: true });
diff --git a/dist/tween.cjs b/dist/tween.cjs
index 5c25edb8..bcbd0bef 100644
--- a/dist/tween.cjs
+++ b/dist/tween.cjs
@@ -217,7 +217,13 @@ var Easing = Object.freeze({
     },
 });
 
-var now = function () { return performance.now(); };
+var _nowFunc = function () { return performance.now(); };
+var now = function () {
+    return _nowFunc();
+};
+function setNow(nowFunction) {
+    _nowFunc = nowFunction;
+}
 
 /**
  * Controlling groups of tweens
@@ -1141,6 +1147,7 @@ var exports$1 = {
     Group: Group,
     Interpolation: Interpolation,
     now: now,
+    setNow: setNow,
     Sequence: Sequence,
     nextId: nextId,
     Tween: Tween,
@@ -1400,4 +1407,5 @@ exports.nextId = nextId;
 exports.now = now;
 exports.remove = remove;
 exports.removeAll = removeAll;
+exports.setNow = setNow;
 exports.update = update;
diff --git a/dist/tween.d.ts b/dist/tween.d.ts
index cb192a9b..d1c2d202 100644
--- a/dist/tween.d.ts
+++ b/dist/tween.d.ts
@@ -184,6 +184,7 @@ declare class Group {
 }
 
 declare const now: () => number;
+declare function setNow(nowFunction: Function): void;
 
 /**
  * Utils
@@ -470,6 +471,7 @@ declare const exports: {
         };
     };
     now: () => number;
+    setNow: typeof setNow;
     Sequence: typeof Sequence;
     nextId: typeof Sequence.nextId;
     Tween: typeof Tween;
@@ -719,4 +721,4 @@ declare const exports: {
     };
 };
 
-export { Easing, Group, Interpolation, Sequence, Tween, VERSION, add, exports as default, getAll, nextId, now, remove, removeAll, update };
+export { Easing, Group, Interpolation, Sequence, Tween, VERSION, add, exports as default, getAll, nextId, now, remove, removeAll, setNow, update };
diff --git a/dist/tween.esm.js b/dist/tween.esm.js
index e87520da..8daaffca 100644
--- a/dist/tween.esm.js
+++ b/dist/tween.esm.js
@@ -213,7 +213,13 @@ var Easing = Object.freeze({
     },
 });
 
-var now = function () { return performance.now(); };
+var _nowFunc = function () { return performance.now(); };
+var now = function () {
+    return _nowFunc();
+};
+function setNow(nowFunction) {
+    _nowFunc = nowFunction;
+}
 
 /**
  * Controlling groups of tweens
@@ -1137,6 +1143,7 @@ var exports = {
     Group: Group,
     Interpolation: Interpolation,
     now: now,
+    setNow: setNow,
     Sequence: Sequence,
     nextId: nextId,
     Tween: Tween,
@@ -1383,4 +1390,4 @@ var exports = {
     update: update,
 };
 
-export { Easing, Group, Interpolation, Sequence, Tween, VERSION, add, exports as default, getAll, nextId, now, remove, removeAll, update };
+export { Easing, Group, Interpolation, Sequence, Tween, VERSION, add, exports as default, getAll, nextId, now, remove, removeAll, setNow, update };
diff --git a/dist/tween.umd.js b/dist/tween.umd.js
index b3bd4cdb..dd511ca8 100644
--- a/dist/tween.umd.js
+++ b/dist/tween.umd.js
@@ -219,7 +219,13 @@
         },
     });
 
-    var now = function () { return performance.now(); };
+    var _nowFunc = function () { return performance.now(); };
+    var now = function () {
+        return _nowFunc();
+    };
+    function setNow(nowFunction) {
+        _nowFunc = nowFunction;
+    }
 
     /**
      * Controlling groups of tweens
@@ -1143,6 +1149,7 @@
         Group: Group,
         Interpolation: Interpolation,
         now: now,
+        setNow: setNow,
         Sequence: Sequence,
         nextId: nextId,
         Tween: Tween,
@@ -1402,6 +1409,7 @@
     exports.now = now;
     exports.remove = remove;
     exports.removeAll = removeAll;
+    exports.setNow = setNow;
     exports.update = update;
 
     Object.defineProperty(exports, '__esModule', { value: true });
diff --git a/docs/user_guide.md b/docs/user_guide.md
index 999813aa..f53a9f33 100644
--- a/docs/user_guide.md
+++ b/docs/user_guide.md
@@ -642,6 +642,12 @@ Note that the interpolation function is global to all properties that are tweene
 
 Check [06_array_interpolation](../examples/06_array_interpolation.html) for an example.
 
+## Changing the Definition of "Now"
+
+When working with tweening, you inevitably rely on a definition of what "now" is. By default, Tween.js uses performance.now, which is a reliable and precise approach. However, if you need to adjust the flow of time—for instance, to slow it down or manipulate it for a custom purpose—you may encounter discrepancies between your internal definition of "now" and what Tween.js considers "now."
+
+To address this, a new function, setNow, has been introduced. This function allows you to redefine the internal "now" used by Tween.js. You can pass a custom function to setNow, which will replace the default definition. This provides greater flexibility and enables synchronization with your specific requirements for time control.
+
 ## Getting the best performance
 
 While Tween.js tries to be performant on its own, nothing prevents you from using it in a way that is counterperformant. Here are some of the ways you can avoid slowing down your projects when using Tween.js (or when animating in the web, in general).
diff --git a/scripts/write-version.js b/scripts/write-version.js
index 6048e673..b811da1a 100644
--- a/scripts/write-version.js
+++ b/scripts/write-version.js
@@ -1,5 +1,5 @@
 import fs from 'fs'
-import pkg from '../package.json' assert {type: 'json'}
+import pkg from '../package.json' with {type: 'json'}
 
 const {version} = pkg
 
diff --git a/src/Index.ts b/src/Index.ts
index 3755cd97..93bd5233 100644
--- a/src/Index.ts
+++ b/src/Index.ts
@@ -10,7 +10,7 @@
 import Easing from './Easing'
 import Group from './Group'
 import Interpolation from './Interpolation'
-import now from './Now'
+import now, { setNow } from './Now'
 import Sequence from './Sequence'
 import Tween from './Tween'
 import VERSION from './Version'
@@ -273,13 +273,14 @@ const update = TWEEN.update.bind(TWEEN)
 
 // NOTE! Make sure both lists of exports below are kept in sync:
 
-export {Easing, Group, Interpolation, now, Sequence, nextId, Tween, VERSION, getAll, removeAll, add, remove, update}
+export {Easing, Group, Interpolation, now, setNow, Sequence, nextId, Tween, VERSION, getAll, removeAll, add, remove, update}
 
 const exports = {
 	Easing,
 	Group,
 	Interpolation,
 	now,
+	setNow,
 	Sequence,
 	nextId,
 	Tween,
diff --git a/src/Now.ts b/src/Now.ts
index 9b51feeb..7a3d935b 100644
--- a/src/Now.ts
+++ b/src/Now.ts
@@ -1,3 +1,11 @@
-const now = (): number => performance.now()
+let _nowFunc: Function = () => performance.now()
+
+const now = (): number => {
+  return _nowFunc()
+}
+
+export function setNow(nowFunction: Function) {
+  _nowFunc = nowFunction
+}
 
 export default now