Roemischer Kalender auss der Geometrica auff alle jar sampt den beweglichen und unbeweglichen Festen nach den Sontags Buchstaben zuverstehen.
- Author: Anonymous
- Publication place: [?Nuremberg or Augsburg
- Publication date: second half of 16th century].
- Physical description: Woodcut and typographic broadside, seven lines of letterpress text, large central woodcut roundel illustrated with signs of the zodiac, sun and moon phases space, topographical panorama, and feast days, volvelle at centre, two smaller roundels in lower corners, type-ornament border within outermost black border, coloured and heightened in gold by a contemporary hand, thick paper, the volvelle printed on paste-paper, verso of edges strengthened, a few neat tears repaired on verso, a few small areas of loss, some colour lightly rubbed.
- Dimensions: 458 by 347mm. (18 by 13.75 inches).
- Inventory reference: 2085
1. outermost two circles: Sunday letters, feast days.
2. next three circles: days of the month, months, zodiacal signs, showing longitude of sun in the zodiacal signs over the course of the year, starting with Sun at beginning of Aries on 10 March.
3. next two circles: lengths of day, depending on the hours of sunrise/sunset, and the hours of the day in Roman numerals. For example, if the sun rises at 8 a.m. (on left) and sets at 4 p.m. (on right), the day length will be eight hours.
4. next ten circles, with moving central volvelle with attached sector, divided into “nachtlenge” (lower pink section) and “tagelenge” (upper yellow section). For example, for the outermost circle, from 15 May through 11 July, the sun rises at 4 a.m. and sets at 9 p.m. giving a day length of 17 hours. The pointer on the volvelle is set to the hour of the mechanical clock (the “grosse uhr”) and then read on the yellow or the pink sections the hour of the day or night, as counted from sunset or sunrise (the “kleine uhr”). Nuremberg counted hours starting at sunrise. Many towns to the east counted hours starting at sunset (Bohemian or Italian hours). The volvelle and the 10 circles permit conversion between these 3 hour-counting schemes, shifting through 9 sections of the year to adjust for the varying day lengths.
5. Small, lower right circle, “Planetenstund”, illustrates which planet is ruling each hour of the day, as day lengths shift from 16 down to 8 hours. The other small, lower left circle calculates the Sunday letter for any year. The instructions say to start counting at the cross, but do not indicate what year this is. The “Schaltjar 25” is confusing, since 1524 was the Schaltjar. The cross should be 1557, 1585 or 1613.