The clock of the Duomo in Florence is one of the oldest functional mechanical clocks. The dial is a fresco painted by one of the greatest artists of the Renaissance, Paolo Uccello. The clock is one of only a few examples in the world that marks the Italic hour, measuring time from sunset to sunset. Thus, “Paolo Uccello’s clock” is both a timepiece and a work of art.
The clock is located in a cavity of the front facade of the Duomo of Florence, above the main entrance. It is reached by a separate door, positioned to the right of the main entrance, through a steep and narrow staircase.
The Fresco by Paolo Uccello
Thanks to Giorgio Vasari, we know that Paolo Uccello painted the facade in 1433 and that it measures almost seven feet in diameter. On the dial each of the 24 hours are painted counterclockwise in Roman numerals. At the center of a blue disc is a golden star. The radius with the ball on its tip rotates counterclockwise throughout the white areas arranged radially.
They are inscribed in a square whose four corners are filled with four mysterious heads of men with halos appearing to look toward the center and down. According to some, they are prophets; for others, the four Evangelists.
The original clock mechanism was designed in 1443 by the Florentine watchmaker Angelo di Niccolò; unfortunately, we don’t have any definite information about this mechanism: it was most likely put together according to a system of checks and balances, some of which were found in a compartment of the Cathedral.
A few decades after the construction, the device was in need of repair, and the Della Volpaia, a family of watchmakers and scientists, agreed to perform the task. In the centuries that followed, various restorations and the replacement of components took place.
The clock regained its original features only four decades ago thanks to a restoration that has brought to light the beautiful dial and restored the old operation of the mechanism, with the hand that marks each of the 24 hours starting from sunset in a counterclockwise motion.The charge lasts up to one week.
The Italic Hour
The Italic Hour is a system that calculates the hours of a day from sunset to sunset, and the 24th hour is not midnight but the hour of the setting of the sun. This manner of measuring time was called “Julian” after Julius Caesar, who promulgated the calendar in 46 BC. It is also called The time of Ave Maria or The Italian time.
It is almost opposite to modern timepieces and must therefore be adjusted throughout the year so that the last hour always occurs at sunset: the needle marks the time from after sunset to correspond with the twenty-fourth hour.
These clocks that followed the solar arc often found themselves on churches and cloisters of monasteries and were used primarily to refer to and measure the various moments of the day that had to be devoted to prayer.
A system similar to that of the Duomo in Florence is that of the Clock Tower in St. Mark’s Square in Venice, which dates from the late fifteenth century.
The Italic hour was replaced after the eighteenth century by the so-called French time, the one used today, which comprises the twelve a.m. and p.m. hours. The adoption of this method was favored by the spread of mechanical clocks which to be set on the Italic time required continuous maintenance. The transition to the French system was final under the rule of Napoleon.
After the last renovation entrusted to the top experts in the field, the clock is finally back to its place on the inner facade of the Church of Santa Maria del Fiore, the Florence Cathedral, above the main entrance.
Pictures by Antonio Quattrone