I N G E N I E U R P E R P E T U A L C A L E N D A R D I G I TA L D AT E - M O N T H
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the local time of your destination before 8 p.m. You must not
turn the hands back between 8 p.m. and 2 a.m. This is because
the calendar does not move backwards by one 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 one day for a second
time and thus indicating one 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, 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 indicate 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.
