Some time zones do not have full-hour time differential factor (TDF). For
example, if you live in Adelaide, Australia, your TDF is actually +9:30 or
+10:30. To see how complex this issue is, refer to
This is further complicated by having to rely on the local machine being set
correctly in the first place (I recently got an e-mail that "showed" it had been
sent March 6, 1998!)...