diff --git a/date/date_c.php b/date/date_c.php
index ba86fb9d2..dd39e20d0 100644
--- a/date/date_c.php
+++ b/date/date_c.php
@@ -113,6 +113,7 @@ public function diff(
* Returns the formatted date string on success or FALSE on failure.
* Since PHP8, it always returns STRING.
*/
+ #[Pure]
#[TentativeType]
public function format(#[LanguageLevelTypeAware(['8.0' => 'string'], default: '')] $format): string;
@@ -430,6 +431,7 @@ public function diff(
* @return string
* Returns the formatted date string on success or FALSE on failure.
*/
+ #[Pure]
#[TentativeType]
public function format(#[LanguageLevelTypeAware(['8.0' => 'string'], default: '')] $format): string {}
@@ -654,6 +656,7 @@ public function __wakeup(): void {}
* @return string
* @link https://php.net/manual/en/datetime.format.php
*/
+ #[Pure]
#[TentativeType]
public function format(#[LanguageLevelTypeAware(['8.0' => 'string'], default: '')] $format): string {}