AN OTTOMAN DESKTOP PERPETUAL CALENDAR MADE FOR SELIM HALIL "EL-REIS", 19TH CENTURY

Two circular disks/dials (dia. Approx. 11 cm) connected by a bar and mounted on a pedestal.
This 19th century Ottoman desktop perpetual calendar appears to be modelled after an European example, of which many examples survive, albeit in a smaller medal form. The calendar consists of two circular disks connected by a rectangular bar. The calendar is connected to a pedestal by means of a small brass tube connector piercing the middle of the connecting bar in an inclined angle.

The first disk bears a table with two columns. The first column shows the symbols and the corresponding Arabic names of the planets which are associated with the days of the week. The next column indicates the days of the week in Arabic. Next to the table, the disk also features a slot though which the date for the days of the month can be seen, aligning with the corresponding names of the days of the week. The disk also features an inscription bearing a name, “Selim Halil el-Reis”, probably the person for whom this perpetual calendar was made.

The second disk features three concentric circles with engravings and corresponding slots. The largest first circle bears an inscription “al-Ruzname al-Dahriyya”, which translates as “Perpetual Calendar”. Opposite to the inscription on the same circle band, there is another inscription reading “Hisâb Shamsî”, which translates as “Solar Calculation” or “Calculation according to the Solar Calendar”. On both sides of the slot with the open end there are two inscriptions which are cut half by the slot.

The first inscription on top reads ‘Ism [Eng. : Month, on the right] + al-Shahr [Eng : The month, on the left] which taken together translates as “The name of the month”. The second line reads Mawqi’ [ Eng. : Position] + al-Shams [ Eng.: The Sun] which, translates as the “position of the Sun”.

The circle underneath, which bears the inscriptions shown through the slot, features for every month the number of the month [1-12], the name of the corresponding Gregorian month [ Kanun al-awwal, Kanun al-Thani, Shabat, Nisan..etc], and the number of days in that particular month. The second line starts with a small depiction of the zodiac signs, the corresponding Arabic name of that sign and the number of the day on which that sign starts.

The second circle band in the middle has two inscriptions “mu’addal tul al-nahar”, the average length of the day, and “mua’ddal tul al-layl”, the average length of the night. Both inscriptions are followed by two arrows indicating the slot where the user should look.

The smallest circle band features, in a similar way as above, two inscriptions: “nisf al-nahar”, midday, and “nisf al-layl”, midnight, again with arrows indicating the slot where the user should look.

LITERATURE
For detailed information on the European tradition of perpetual calendars in medal form see:
Silke Ackermann, “Maths and Memory: Calendar Medals in the British Museum (Part I)”, The Medal, 45 (Autumn 2004), pp. 3-43.
Silke Ackermann, “Maths and Memory: Calendar Medals in the British Museum (Part II)”, The Medal, 46 (Spring 2005), pp. 3-22.