iwc PORTUGIESER PERPETUAL CALENDAR TOURBILLON Operating Instructions Manual page 18

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moon can occur at any time of night
or day, it may be that your watch dis­
plays the calendar date of the full or
new moon but that the moon phase
display has not reached this pos ition
due to the exact time of the full or
new moon. IWC sets the moon phase
display so that it displays the full and
new moon precisely on as many dates
in the year as possible.
P O R T U G I E S E R P E R P E T U A L C A L E N D A R T O U R B I L L O N