diff --git a/packages/block-library/src/post-date/edit.js b/packages/block-library/src/post-date/edit.js
index 8b0ce36ad168b6..9cc90f3d61dbee 100644
--- a/packages/block-library/src/post-date/edit.js
+++ b/packages/block-library/src/post-date/edit.js
@@ -99,11 +99,15 @@ export default function PostDateEdit( props ) {
 
 	const blockEditingMode = useBlockEditingMode();
 
+	const validDatetime = datetime || new Date();
 	let postDate = (
-		<time dateTime={ dateI18n( 'c', datetime ) } ref={ setPopoverAnchor }>
+		<time
+			dateTime={ dateI18n( 'c', validDatetime ) }
+			ref={ setPopoverAnchor }
+		>
 			{ format === 'human-diff'
-				? humanTimeDiff( datetime )
-				: dateI18n( format || siteFormat, datetime ) }
+				? humanTimeDiff( validDatetime )
+				: dateI18n( format || siteFormat, validDatetime ) }
 		</time>
 	);
 
diff --git a/packages/date/src/index.ts b/packages/date/src/index.ts
index fae4e3ecba70d8..0daf9e7a63b1b6 100644
--- a/packages/date/src/index.ts
+++ b/packages/date/src/index.ts
@@ -626,7 +626,7 @@ export function humanTimeDiff(
  * @return A moment instance.
  */
 function buildMoment(
-	dateValue?: Moment | Date | string | number,
+	dateValue: Moment | Date | string | number,
 	timezone: string | number = ''
 ) {
 	const dateMoment = momentLib( dateValue );