diff --git a/src/Surfnet/Stepup/DateTime/DateTime.php b/src/Surfnet/Stepup/DateTime/DateTime.php
index 4a038ec1b..e04cec687 100644
--- a/src/Surfnet/Stepup/DateTime/DateTime.php
+++ b/src/Surfnet/Stepup/DateTime/DateTime.php
@@ -35,6 +35,7 @@ class DateTime implements Stringable
      * `DateTime::createFromString()`.
      */
     public const FORMAT = 'Y-m-d\\TH:i:sP';
+    public const MAIL_FORMAT = 'Y-m-d H:i:s';
 
     /**
      * Allows for mocking of time.
diff --git a/src/Surfnet/StepupMiddleware/CommandHandlingBundle/Identity/Service/RegistrationMailService.php b/src/Surfnet/StepupMiddleware/CommandHandlingBundle/Identity/Service/RegistrationMailService.php
index 5fac5c732..2d94876b2 100644
--- a/src/Surfnet/StepupMiddleware/CommandHandlingBundle/Identity/Service/RegistrationMailService.php
+++ b/src/Surfnet/StepupMiddleware/CommandHandlingBundle/Identity/Service/RegistrationMailService.php
@@ -158,7 +158,7 @@ private function sendRegistrationEmailWithRas(
             'commonName' => $commonName,
             'emailAddress' => $email,
             'registrationCode' => $registrationCode,
-            'expirationDate' => $expirationDate,
+            'expirationDate' => $expirationDate->format(DateTime::MAIL_FORMAT),
             'ras' => $ras,
             'selfServiceUrl' => $this->selfServiceUrl,
         ];
@@ -208,7 +208,7 @@ private function sendRegistrationEmailWithRaLocations(
             'commonName' => $commonName,
             'emailAddress' => $email,
             'registrationCode' => $registrationCode,
-            'expirationDate' => $expirationDate,
+            'expirationDate' => $expirationDate->format(DateTime::MAIL_FORMAT),
             'raLocations' => $raLocations,
             'selfServiceUrl' => $this->selfServiceUrl,
         ];
diff --git a/src/Surfnet/StepupMiddleware/MiddlewareBundle/Service/VerifiedSecondFactorReminderMailService.php b/src/Surfnet/StepupMiddleware/MiddlewareBundle/Service/VerifiedSecondFactorReminderMailService.php
index a8f9d296a..19df90d0d 100644
--- a/src/Surfnet/StepupMiddleware/MiddlewareBundle/Service/VerifiedSecondFactorReminderMailService.php
+++ b/src/Surfnet/StepupMiddleware/MiddlewareBundle/Service/VerifiedSecondFactorReminderMailService.php
@@ -131,7 +131,7 @@ private function sendReminderWithInstitution(
             'templateString' => $emailTemplate->htmlContent,
             'locale' => $locale,
             'commonName' => $commonName,
-            'expirationDate' => $requestedAt,
+            'expirationDate' => $requestedAt->format(DateTime::MAIL_FORMAT),
             'registrationCode' => $registrationCode,
             'raLocations' => $raLocations,
         ];
@@ -153,7 +153,7 @@ private function sendReminderWithRas(
         string $locale,
         string $commonName,
         string $email,
-        DateTime$requestedAt,
+        DateTime $requestedAt,
         string $registrationCode,
         array $ras,
     ): void {
@@ -174,7 +174,7 @@ private function sendReminderWithRas(
             'templateString' => $emailTemplate->htmlContent,
             'locale' => $locale,
             'commonName' => $commonName,
-            'expirationDate' => $requestedAt,
+            'expirationDate' => $requestedAt->format(DateTime::MAIL_FORMAT),
             'registrationCode' => $registrationCode,
             'ras' => $ras,
         ];