The next backstage build will change the way Tinderbox reads dates from its XML files, and the way is parses ISO-8601 dates like “2019-02-28T12:00:00-04:00”.
Currently: when reading documents, Tinderbox assumes that times were saved in the current local timezone.
Future: on macOS 10.12 and later, Tinderbox will respect the time zone of the date in saved documents, and will also recognize the time zone when assigning an ISO8601 date string to a date attribute. On 10.10 and 10.11, the old behavior will be retained.