Ok, this is now implemented in latest CBSubs build release. You can use [SUBSCRIPTION_EXPIRY_DATE_UTC] to get the raw database datetime for subscription expiration date. I recommend saving it to a datetime field then using the datetime fields built in format parameters to reformat it however you like and enable/disable timezone offset as desired. It can also be ran though [cb:date], but again [cb:date] applies timezone offset so please keep that in mind.