The square disc of the clock comprisesof slightly more than 16 m2. With the exeption of the margin and the symbols of the Evangelists in the corner the date of origin is 1472.
The concentric circles with numerals and carved figures, the hands and the discs are striking. They provide a basis for indicating the time as well as the astronomic and astrologic details.
A. The indication of the time. The indication of the time here is done in an unusual way. That is why a seemingly simple reading of the time can become difficult:
At first there is the ring that indicates the hours. It is a gothic ring of numbers with twice the cyphers 1 to 12 (1, II, III, 1111, V, VI, VII, VIII, IX, X, XI, XII). Secondly the the Clock has a hand that indicates the hours, but not one that indicates the minutes. It turns around once a day and it is a double hand. With both ends it extends into the ring that indicates the hours. This means that you can read the time in the following way: on one end of the hand (in the daytime in the above half of the disc) and at the star at the other end (in the daytime in the below half of the disc). B. The astronomic and astrologic details. Within the ring that indicates the hours there are two wide rings of figures and two small rings that indicate the numerals. Moreover, there are two circular discs with a hand each turning around the centre of the disc of the Clock.
The external one of the two wide rings of figures is the ring with the carved signs of the zodiac. The small ring of numerals located between the ring of hours and the ring of the zodiac devides each sign of the zodiac from 5 to 5 degrees to 30 degrees.
The sign of the Aries is located right across. In anti-clockwise direction it is followed by the signs of the Taurus, the Gemini, the Cancer, the Leo, the Virgo, the Libra, the Scorpio, the Sagittarius, the Capricorn, the Aquarius and the Volans.
Inwards next to the ring of the zodiacs there is another ring with carved pictures that refer to the months. Each month is represented by a typical illustration. It starts with the January below on the right hand side and runs opposite the clockwise direction:
An elegant gentleman is dining. A man is warming himself at the fire.
A man is planting two trees. A woman is digging the soil.
A farmer is seeding. A mower is cutting grass with a scythe.
A female farmer is cutting corn with a sickle.
A farmer is threshing corn with a flail. A winegrower is harvesting vines. A man is picking apples.
A man is cutting wood. A man is killing a pig.
In the centre of the disc of the Clock there are two discs that turn around: The visible one in front is painted with stars and a dragon and it has a circular sector which is the disc of the sun. A hand that indicates the position of the sun is fixed on the margin. This disc rotates once a year opposite the clockwise direction. The hand that indicates the position of the sun passes through all the signs of the zodiac and signs of the months. It shows the position of the sun in the signs of the zodiac and the approximate date.
The disc that indicates the phases of the moon is located underneath the disc that indicates the position of the sun. A part of it you can see in the sector of the disc that displays the position of the sun. There the current phase of the moon is shown: If there is full moon you can see a bright moon face. At new moon there is a dark moon face and at other times you can find a more or less large piece of the golden yellow moon according to the phase of the moon.
The disc that indicates the phases of the moon turns around 360 degrees in 27.32 days (= sidereal month). The hand that is fixed on it passes through all signs of the zodiac. In the meantime the hand that indicates the position of the sun has moved in the same direction. This way 29.53 days pass until both hands overlap (= 1 synodal month. In nature it corresponds to the period of two succeeding similar phases of the moon.
At the edge of the disc that indicates the position of the sun there is a small ring of numerals with the numbers from 1 to 29. The location of the hand that displays the phases of the moon gives information about the "age of the moon". It means the number of days that have passed since the last new moon.
If there is new moon (Age 0 days) both hands overlap. At full moon (Age around 15 days) they are located opposite each other. At waxing or waning moon they form a right angle.
C. The discs on the hand that indicate the hours. There is another disc on each half of this disc. Both you can turn on the hand. On the margin below there are weights fastened behind each disc which guarantee a certain position. In the daytime the disc below shows Senator Zacharias Sebes (*1601 in Zellerfeld, +1650 in Rostock). He rendered outstanding services to reconstruct the Clock in 1641/43. His picture was created in commemoration of his efforts. On the margin of the "Sebes-disc" a 24-ring of numerals passes the disc that indicates the hours which makes it possible to read the time from this point as well. This “gravity clock“ is a miniature clock: a clock on a clock. Presumably this clock was built in 1472 carrying a different picture until 1650.
The disc on the other half (which is positioned above in the daytime) is an astrologic "hour-regency-clock". In contrast to the "Sebes-disc" this disc is moved by means of a gear. That makes it possible that every hour one of the 28 sectors passes the red hand that goes in direction to the hand that indicates the hours. Each of the 28 sectors is labelled with the name and the sign of one of the seven planets. According to the Ptolemaic system these planets used to be the Mercury, the Venus, the Mars, the Jupiter, the Saturn as well as the Sun and the Moon. Under the red hand there is the sector of the orb that rules the current hour ("hour ruler"). The ruler of the first hour after midnight is also the ruler of the day ("possessor") and gives name to the beginning day:
Sonne(Sun) - Sonntag (engl. Sunday) Mond (Moon)- Montag (engl. Monday, frz. lundi) Mars (Tiu) - Dienstag (engl. Tuesday, frz. mardi) Merkur (Mercur, Wodan) - Mittwoch (engl. Wednesday, frz. mercredi) Jupiter (Thor) - Donnerstag (engl. Thursday, frz. jeudi) Venus (Freya) - Freitag (engl. Friday, frz. vendredi) Saturn - Sonnabend (engl. Saturday)
After the Reformation the symbols of the Evangelists were added:
Matthew as an angel (left above) Marcus as a winged lion (left below) John as an eagle (right above) Luke as a winged bull (right below)
The attentive observer notices that the figures do not originate from 1472, because the two above are located on doors which lost its original function in 1641/43.
This detail is an important evidence for the close relation between the Clock in Danzig and the one in Rostock. The Clock in Danzig still has its original design from 1463/70. It still has the two doors in the above spandrel of the clock disc. They open at certain times and you can see two biblical scences: The Annunciation of the Angel to Mary (Lk. 1, 26-38) and the Adoration of the Magi (Mt. 2, 1-2). These two and other analogies between the two Clocks give reason to think that the doors in Rostock had a similar function. With the end of the worship of Mary after the Reformation this scene was not up to date anymore. At the reconstruction during the Thirty Years‘ War it was replaced by the Evangelists.
Furthermore, one can suggest that there was an upper part above the clock disc in 1472. It was similar the one in Danzig (Rotation of the Apostles and Evangelists, Adam and Eve). It degenerated in the 16 and 17 century and was replaced by the current one in 1641/43.