User:Alkas96/Portable Byzantine Sundial Calendar

The Byzantine Sundial Calendar, is a portable sundial and calendar from the early Byzantine era. It is on display on London's Science Museum and just like the Antikythera mechanism, it can "show" the time and day in 16 different cities-regions of the known world in Greek as well as the relative positions of the sun and moon and the phases of the moon. It was purchased from a private individual who stated that he acquired it in Lebanon. It is dated to the second half of the 5th century AD or the beginning of the 6th century AD. It is made of brass (bronze) and has the shape of a disk with a diameter of 13.5 cm and a depth of about 1.5 cm. Its front circular surface bears in two semicircles the names of the months of the Julian Calendar (the same as today's), and in smaller circle the symbols of the days of the week (heads of deities). It also has the names of the main cities of the time in Greek script, such as Rome, Constantinople, Rhodes, etc., in a circle. together with their latitude in degrees, also in Greek numerals. This disc is also typical of other portable sundials of the era. What makes this particular watch special is that it has a ratcheting axle and gear system inside, part of a system that showed the phase of the Moon, the day of the month and the position of the Sun in the zodiac. Four gears and two axles are preserved. This mechanism resembles a similar mechanism described by al-Biruni around the year 1000 AD. The back surface of the mechanism is missing and only hypothetical representations of it have been made. After the Antikythera Mechanism, it is the second oldest cog mechanism found.

The discovery of this Byzantine mechanism shows that the Hellenistic tradition attested by the Mechanism of Antikythera (1st century BC) continued actively in the Byzantine era and probably influenced the corresponding Islamic tradition. It also shows the inadequacy of the information contained in the written sources.