iwc Schaffhausen Mode D'emploi page 24

Crossing time zones and date lines with the
Portuguese Perpetual Calendar
Setting when crossing time zones:
• When crossing time zones in an easterly direction, you should simply set
the time forwards to the new local time.
• If time zones are crossed in a westerly direction, you can set the hands
of your watch backwards to the actual time of day. When doing this, how-
ever, you must not exceed the end of the change phase of the perpetual
calendar, that is to say 2.00. If this situation occurs, when travelling to
the west, you must set the local time of your destination before 20.00.
Under no circumstances may the hands be turned back between 20.00
and 2.00.