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Milan Duomo Sundial was built in 1786, by the astronomers of Brera, in agreement with the Veneranda Fabbrica del Duomo and the Metropolitan Chapter.
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It consists of a thin brass line, visible on the floor when entering through the façade doors, at the entranceway of the Cathedral.
Meridian sundialVeneranda Fabbrica del Duomo di Milano
Either side of the line, there are marble tiles featuring the 12 zodiac signs, which help to interpret the season of the year.
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Sunlight enters the gnomon hole carved into the ceiling, 24 metres high on the southern first aisle, allowing the light to project onto the line which spans the entire length of the Monument. The ray of light indicates solar noon.
Duomo meridian sundial, detailVeneranda Fabbrica del Duomo di Milano
A Candoglia marble plaque, depicting the zodiacal sign corresponding to the winter solstice, Capricorn, is inserted on the northern wall of the Cathedral.
Duomo meridian sundial, detailVeneranda Fabbrica del Duomo di Milano
As part of the reform of time requested by the Habsburg government, the decision to build a sundial in the Duomo was necessary to standardize calculation of the hours from midday.
An initiative that was particularly significant as it marked an important change in the method of measuring time, which until then had been calculated starting from sunset.
Duomo meridian sundial, detailVeneranda Fabbrica del Duomo di Milano
An imperial decree had set December 1, 1786 as the date on which they would switch to transalpine time (or French time), which counted the hours from true midday which would have been indicated by the sundial placed inside Milan Duomo.
A curious feature
At solar noon, indicated by the beam of light on the brass line, a signal was given from the Duomo parvis, towards the Tower of the Giureconsulti Palace; from there a designated person alerted Sforzesco Castle, where cannon fire announced solar noon to the city.
Read more on Milan Cathedral Remixed.
