A vertical sundial on the north wing of a large (lower) cloister. Fr. Stipe Nosić says the following about the sundial:
This sundial is characterized by the fact that it has two dials and measures time in two different ways of calculating. The upper dial shows the time according to Roman calculation of the hour of the day. Their day consisted of vigils (lat. Vigilia = vigil), night guards, who alternated four times for three hours from sunset to sunrise. After twelve hours of the night (hora duodecima noctis) the sun rose, so the first hour of the day was an hour after sunrise. The sixth hour from then (hora sexta) was at noon, and after the twelfth hour of the day (hora duodecima diei) it was sunset, and thus a new day began. The upper hour is marked on the upper clock, so it has a dial with marked Roman numerals (from VIII to XII and from I to VI), and uses the sun to measure the time from 7 to 18 hours.
The lower dial measures time in a newer way, the so-called "Italian", which began to be applied in the new century. According to this method of calculation, a day has 24 hours, with the hours being counted from sunset. The dial on the lower dial has Arabic numerals from 16 to 22, which means that this calculation shows the time for only seven hours a day.
In sunny weather, the time on both dials is marked by a shadow of a pointer made of wrought iron. It consists of an inclined iron rod, at the end of which is a tin-toothed sun with a hole in the middle. An iron support, placed perpendicular to the surface of the painting, supports the pointer. When the pointer on the upper dial marks 12 o'clock (noon) with its shadow, its shadow together with the jagged pierced tin sun on the lower dial marks the sixteenth hour of the day. It depends on the season between 3pm and 5pm, according to today’s counting method. The Italian way of counting hours remained in some places until the 19th century, when it was generally accepted to count hours in the day from midnight to 24 hours. Since then, the dials usually have marked hours from midnight to noon (12 hours) and from noon to midnight (12 hours).
It is noticeable that the line on the upper dial divides the daily part of the day in half, which marks 12 o'clock local time, goes vertically. This reveals that the wall of the building on which the sundial is painted is placed exactly to the north.
We thank Fr. Stipe Nosić for the provided text and photographs.
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