PORTUGIESER PERPETUAL CALENDAR 42
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Setting when crossing time zones:
– When crossing time zones in an easterly direction, you should simply set the time forward to the
new local time.
– When crossing time zones in a westerly direction, you can set the hands of your watch back to the
actual time of day. When doing this, however, you must not move back into the calendar’s auto-
matic switching phase, i.e. beyond 2 a.m. If this situation occurs when you are travelling west, you
should set the local time of your destination before 10 p.m.
You must not turn the hands back
between 10 p.m. and 2 a.m.
This is because the calendar does not move backwards by 1 day
when the hands are turned back beyond midnight, but remains on the same day. If you go past the
end of the calendar’s switching phase (i.e. beyond 2 a.m.) when turning the hands back, you run
the risk of the calendar advancing by 1 day for a second time and thus indicating 1 day too many.
Setting when crossing the International Date Line:
– When crossing the International Date Line in a westerly direction (you enter the next day, regard-
less of the time of day), simply turn the time forward 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, regard-
less of the time of day), you must likewise set your watch forward to the new local time. However,
your watch will now indicate the wrong date (1 day too many). This incorrect date indication can be
corrected by resetting the hands twice, by 12 hours on each occasion:
