We are deploying a custom timezone on all our systems, but exchange appears to use it's own internal timezones. Is it possible to create a custom exchange timezone and set it as the default timezone on all new and existing mailboxes? For years we have been using a timezone with the wrong UTC offset. This is because we have no timezone for the Falkland Islands on Microsoft products. We contacted Microsoft many years ago about having Falkland Islands time added but have never had any luck.