What’s a Parapegma?

What you are viewing is a reconstructed timekeeping device from antiquity.

Look closely and you’ll see the signs of the zodiac and the faces of the Roman gods. What does all this mean? The value of this historical object depends  greatly upon our place in time. A person of living in ancient Rome might instantly recognize it and understand its function. An archaeologist would assign it’s worth by how it fits into collections of similar items. And a Dayologist would find the design elements fascinating because they suggest the foundation of Dayology Typology System.

The Actual Artifact

This artifact was discovered in the ruins of the Trajan’s Baths, an elaborate bathing complex located on the Oppian Hill in Rome. This public facility was  constructed in 79-81 A.D. and operated into the early 5th century. This public building was designed by Apollodorus of Damascus and included seven massive cisterns, a fountain room, two libraries, a series of gardens and an art museum complete with decorative frescoes and mosaics. Another source, Robert Odem the author of Sunday in Roman Paganism (page 95) states that the  artifact was found in the baths built by emperor Titus.  He presents the detailed descriptions of Italian archaeologist, G.A. Guattani who obviously had the occasion to examine the item. The history of this particular parapegma is also discussed by Daryn Lehoux (168-70) in Astronomy, Weather, and Calendars in the Ancient World. Here it is said that the artifact was discovered in the early nineteenth century. The location here is given as the baths of Trajan and it is called the Astrological or Thermae Traiani parapegma.

Schematic Diagram

The tablet was mounted in the wall and is identified as a parapegma or a stick calendar. It features pegs which are moved from day to day and month to month. The holes of the month are located on the left and right margins. The holes for the twelve sun signs are found around the zodiac circle. And from Mount Olympus the seven gods are looking down. From left to right, they are: Saturn, the Sun, the Moon, Mars, Mercury, Jupiter and Venus. And beneath each god is its very own hole for a movable peg. The presence of the holes near the twelve signs of the Zodiac and the thirty days of the month mean that the holes beneath of the seven gods represent the seven days of the week.

And if Saturn in the first position and left-hand side  is moved to right side and the end of the list, then the rulers appear in the same order of that most of the world calendars use today. That would be, SUN/Sunday, MOON/Monday, MARS/Tuesday, MERCURY/Wednesday, JUPITER/Thursday, VENUS/Friday, and SATURN/Saturday. Actually the ancients had their own reasons for making Saturday the first day of their week. We will save that interesting story for when we deal with the magical matter of the Planetary Hours.