diff --git a/src/vs/vscode.proposed.d.ts b/src/vs/vscode.proposed.d.ts
index f1489879e81..8b96161afd9 100644
--- a/src/vs/vscode.proposed.d.ts
+++ b/src/vs/vscode.proposed.d.ts
@@ -988,15 +988,16 @@ declare module 'vscode' {
 		// todo@API duplicates status bar API
 		readonly statusMessage?: string;
 
-		constructor(editable?: boolean, breakpointMargin?: boolean, statusMessage?: string, lastRunDuration?: number, inputCollapsed?: boolean, outputCollapsed?: boolean, custom?: Record<string, any>)
+		constructor(editable?: boolean, breakpointMargin?: boolean, statusMessage?: string, inputCollapsed?: boolean, outputCollapsed?: boolean, custom?: Record<string, any>)
 
-		with(change: { editable?: boolean | null, breakpointMargin?: boolean | null, statusMessage?: string | null, lastRunDuration?: number | null, inputCollapsed?: boolean | null, outputCollapsed?: boolean | null, custom?: Record<string, any> | null, }): NotebookCellMetadata;
+		with(change: { editable?: boolean | null, breakpointMargin?: boolean | null, statusMessage?: string | null, inputCollapsed?: boolean | null, outputCollapsed?: boolean | null, custom?: Record<string, any> | null, }): NotebookCellMetadata;
 	}
 
 	export interface NotebookCellExecutionSummary {
 		executionOrder?: number;
 		success?: boolean;
-		duration?: number;
+		startTime?: number;
+		endTime?: number;
 	}
 
 	// todo@API support ids https://github.com/jupyter/enhancement-proposals/blob/master/62-cell-id/cell-id.md
@@ -1648,7 +1649,6 @@ declare module 'vscode' {
 	}
 
 	export interface NotebookCellExecuteStartContext {
-		// TODO@roblou are we concerned about clock issues with this absolute time?
 		/**
 		 * The time that execution began, in milliseconds in the Unix epoch. Used to drive the clock
 		 * that shows for how long a cell has been running. If not given, the clock won't be shown.
@@ -1664,9 +1664,9 @@ declare module 'vscode' {
 		success?: boolean;
 
 		/**
-		 * The total execution time in milliseconds.
+		 * The time that execution finished, in milliseconds in the Unix epoch.
 		 */
-		duration?: number;
+		endTime?: number;
 	}
 
 	/**
diff --git a/src/vs/workbench/api/common/extHostNotebook.ts b/src/vs/workbench/api/common/extHostNotebook.ts
index 68618446c2d..43c6f6df2c3 100644
--- a/src/vs/workbench/api/common/extHostNotebook.ts
+++ b/src/vs/workbench/api/common/extHostNotebook.ts
@@ -1027,7 +1027,6 @@ class NotebookCellExecutionTask extends Disposable {
 		this._executionOrder = _cell.internalMetadata.executionOrder;
 		this.mixinMetadata({
 			runState: extHostTypes.NotebookCellExecutionState.Pending,
-			lastRunDuration: null,
 			executionOrder: null
 		});
 	}
@@ -1105,7 +1104,7 @@ class NotebookCellExecutionTask extends Disposable {
 				that.mixinMetadata({
 					runState: extHostTypes.NotebookCellExecutionState.Idle,
 					lastRunSuccess: result?.success ?? null,
-					lastRunDuration: result?.duration ?? null,
+					runEndTime: result?.endTime ?? null,
 				});
 			},
 
diff --git a/src/vs/workbench/api/common/extHostTypeConverters.ts b/src/vs/workbench/api/common/extHostTypeConverters.ts
index 82c989a0199..18f6adaadcb 100644
--- a/src/vs/workbench/api/common/extHostTypeConverters.ts
+++ b/src/vs/workbench/api/common/extHostTypeConverters.ts
@@ -1437,7 +1437,8 @@ export namespace NotebookDocumentMetadata {
 export namespace NotebookCellPreviousExecutionResult {
 	export function to(data: notebooks.NotebookCellMetadata): vscode.NotebookCellExecutionSummary {
 		return {
-			duration: data.lastRunDuration,
+			startTime: data.runStartTime,
+			endTime: data.runEndTime,
 			executionOrder: data.executionOrder,
 			success: data.lastRunSuccess
 		};
@@ -1446,7 +1447,7 @@ export namespace NotebookCellPreviousExecutionResult {
 	export function from(data: vscode.NotebookCellExecutionSummary): Partial<notebooks.NotebookCellMetadata> {
 		return {
 			lastRunSuccess: data.success,
-			lastRunDuration: data.duration,
+			runEndTime: data.endTime,
 			executionOrder: data.executionOrder
 		};
 	}
@@ -1634,10 +1635,10 @@ export namespace NotebookDocumentContentOptions {
 			transientMetadata: {
 				...options?.transientMetadata,
 				executionOrder: true,
-				lastRunDuration: true,
 				runState: true,
 				runStartTime: true,
 				runStartTimeAdjustment: true,
+				runEndTime: true,
 				lastRunSuccess: true
 			}
 		};
diff --git a/src/vs/workbench/contrib/notebook/browser/contrib/coreActions.ts b/src/vs/workbench/contrib/notebook/browser/contrib/coreActions.ts
index f6983355356..49537cfb0ca 100644
--- a/src/vs/workbench/contrib/notebook/browser/contrib/coreActions.ts
+++ b/src/vs/workbench/contrib/notebook/browser/contrib/coreActions.ts
@@ -1319,7 +1319,7 @@ registerAction2(class extends NotebookCellAction {
 					runState: NotebookCellExecutionState.Idle,
 					runStartTime: undefined,
 					runStartTimeAdjustment: undefined,
-					lastRunDuration: undefined,
+					runEndTime: undefined,
 					statusMessage: undefined,
 					executionOrder: undefined
 				}
diff --git a/src/vs/workbench/contrib/notebook/browser/diff/diffComponents.ts b/src/vs/workbench/contrib/notebook/browser/diff/diffComponents.ts
index ef67f19dd33..3ad6a241475 100644
--- a/src/vs/workbench/contrib/notebook/browser/diff/diffComponents.ts
+++ b/src/vs/workbench/contrib/notebook/browser/diff/diffComponents.ts
@@ -494,7 +494,6 @@ abstract class AbstractElementRenderer extends Disposable {
 						break;
 
 					case 'executionOrder':
-					case 'lastRunDuration':
 						// number
 						if (typeof newMetadataObj[key] === 'number') {
 							result[key] = newMetadataObj[key];
diff --git a/src/vs/workbench/contrib/notebook/browser/view/renderers/cellRenderer.ts b/src/vs/workbench/contrib/notebook/browser/view/renderers/cellRenderer.ts
index cfd93d3dc0d..d944c62e5a7 100644
--- a/src/vs/workbench/contrib/notebook/browser/view/renderers/cellRenderer.ts
+++ b/src/vs/workbench/contrib/notebook/browser/view/renderers/cellRenderer.ts
@@ -848,8 +848,8 @@ export class CodeCellRenderer extends AbstractCellRenderer implements IListRende
 			} else {
 				templateData.timer.clear();
 			}
-		} else if (typeof metadata.lastRunDuration === 'number') {
-			templateData.timer.show(metadata.lastRunDuration);
+		} else if (metadata.runState === NotebookCellExecutionState.Idle && metadata.runStartTime && metadata.runEndTime) {
+			templateData.timer.show(metadata.runEndTime - metadata.runStartTime);
 		} else {
 			templateData.timer.clear();
 		}
diff --git a/src/vs/workbench/contrib/notebook/common/notebookCommon.ts b/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
index 782944efeac..7cbcbffcfc8 100644
--- a/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
+++ b/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
@@ -91,7 +91,7 @@ export interface NotebookCellMetadata {
 	runState?: NotebookCellExecutionState;
 	runStartTime?: number;
 	runStartTimeAdjustment?: number;
-	lastRunDuration?: number;
+	runEndTime?: number;
 	inputCollapsed?: boolean;
 	outputCollapsed?: boolean;
 	custom?: { [key: string]: unknown };