diff --git a/admin_manual/configuration_server/config_sample_php_parameters.rst b/admin_manual/configuration_server/config_sample_php_parameters.rst
index 3471fc218..da8e9f83e 100644
--- a/admin_manual/configuration_server/config_sample_php_parameters.rst
+++ b/admin_manual/configuration_server/config_sample_php_parameters.rst
@@ -840,7 +840,9 @@ Defaults to an empty array.
 
 This uses PHP.date formatting; see http://php.net/manual/en/function.date.php
 
-Defaults to ``Y-m-d\TH:i:sO`` (ISO8601)
+Defaults to ``Y-m-d\TH:i:sP`` (ISO8601 but with colon between hours and
+minutes of the timezone) - see \DateTime::ISO8601
+(https://secure.php.net/manual/en/class.datetime.php#datetime.constants.iso8601)
 
 ::