iwc Portugieser grande Complication Mode D'emploi page 28

Setting when crossing the International Date Line:
• When crossing the International Date Line in a westerly direction (you enter
the next day, regardless of the time of day), simply turn the time forwards to
the new local time, and the date change will take place automatically.
• When crossing the International Date Line in an easterly direction (you enter
the previous day, regardless of the time of day), you must likewise set your
watch forwards to the new local time. However, your watch will now indi-
cate the wrong date (one day too many). This incorrect date indication can
be corrected by resetting the hands twice, by 12 hours on each occasion:
• Setting the watch back by 12 hours during the afternoon between
2 p.m. and 8 p.m. will prevent the calendar from advancing at midnight.
• Setting the watch back another 12 hours the following morning between
2 a.m. and 11 a.m. will synchronize the date display with the local date.