diff --git a/moto/s3/models.py b/moto/s3/models.py
index 98229539e..706d8ad42 100644
--- a/moto/s3/models.py
+++ b/moto/s3/models.py
@@ -788,6 +788,10 @@ class FakeBucket(CloudFormationModel):
     def location(self):
         return self.region_name
 
+    @property
+    def creation_date_ISO8601(self):
+        return iso_8601_datetime_without_milliseconds_s3(self.creation_date)
+
     @property
     def is_versioned(self):
         return self.versioning_status == "Enabled"
diff --git a/moto/s3/responses.py b/moto/s3/responses.py
index 530365a6e..396a53aae 100644
--- a/moto/s3/responses.py
+++ b/moto/s3/responses.py
@@ -1755,7 +1755,7 @@ S3_ALL_BUCKETS = """<ListAllMyBucketsResult xmlns="http://s3.amazonaws.com/doc/2
     {% for bucket in buckets %}
       <Bucket>
         <Name>{{ bucket.name }}</Name>
-        <CreationDate>{{ bucket.creation_date.isoformat() }}</CreationDate>
+        <CreationDate>{{ bucket.creation_date_ISO8601 }}</CreationDate>
       </Bucket>
     {% endfor %}
  </Buckets>