Perpetual Calendar 1526

The first perpetual calendarPerpetual calendarA calendar mechanism that accounts for different month lengths and leap years. wristwatch made in series. Calatrava-style 34 mm case; day and month in two windows below 12, date by hand around the moon phaseMoon-phase displayAn astronomical indication showing the Moon’s changing appearance through its cycle, averaging about 29.5 days. Display accuracy and the interval between corrections depend on the mechanism; a maker’s specification for one calibre should not be applied to every moon-phase watch. at 6. About 210 were made over twelve years.