diff --git a/swh/web/api/views/metadata.py b/swh/web/api/views/metadata.py
--- a/swh/web/api/views/metadata.py
+++ b/swh/web/api/views/metadata.py
@@ -37,14 +37,14 @@
             should be returned
         :query string authority: A metadata authority identifier, formatted as
             ``<type> <IRI>``. Required.
-        :query string after: An ISO representation of the minimum timestamp of metadata
+        :query string after: ISO8601 representation of the minimum timestamp of metadata
             to fetch. Defaults to allowing all metadata.
         :query int limit: Maximum number of metadata objects to return.
 
         {common_headers}
 
         :>jsonarr string target: SWHID of the object described by this metadata
-        :>jsonarr string discovery_date: ISO8601 timestamp of the moment this
+        :>jsonarr string discovery_date: ISO8601/RFC3339 timestamp of the moment this
             metadata was collected.
         :>jsonarr object authority: authority this metadata is coming from
         :>jsonarr object fetcher: tool used to fetch the metadata
diff --git a/swh/web/api/views/origin.py b/swh/web/api/views/origin.py
--- a/swh/web/api/views/origin.py
+++ b/swh/web/api/views/origin.py
@@ -28,7 +28,7 @@
 DOC_RETURN_ORIGIN_ARRAY = DOC_RETURN_ORIGIN.replace(":>json", ":>jsonarr")
 
 DOC_RETURN_ORIGIN_VISIT = """
-        :>json string date: ISO representation of the visit date (in UTC)
+        :>json string date: ISO8601/RFC3339 representation of the visit date (in UTC)
         :>json str origin: the origin canonical url
         :>json string origin_url: link to get information about the origin
         :>jsonarr string snapshot: the snapshot identifier of the visit