I can't seem to sort localisation of the email timestamp generated from a contact form.

I've tried adding to the config/site.php... but seems not to take any notice.

define('APP_TIMEZONE', 'Europe/London');
define('DATE_APP_GENERIC_MDY', 'd-m-Y');
define('LOCALE', 'en_GB');
define ('DATE_DEFAULT_TIMEZONE_SET', 'Europe/London');

(My host is based in Dallas US, but site is a UK site... so emails are timestamped 5hrs behind)

Any help much appreciated.