The "Hebdomas" name refers to the Ancient Greek concept of the end of the week. Also called sabbath or jubilee, Hebdomas could be used as a term for the seventh day or year. Although the famous watch movement had 8-day power reserve, the concept of a watch that would require winding just once a week is what gave it this name.
The original Hebdomas movement is an 8-day hand-winding watch movement. The massive mainspring barrel covers the entire diameter of the movement, rotating around the center similar to an automatic rotor. But perhaps the most recognizable feature of the movement is the exposed balance on the dial side, which is mounted to a dial-side bridge. This is typically gilded and engraved with a decorative floral motif.
The hour and minute hands are set off-center above the balance wheel, giving Hebdomas powered watches a distinctive haute horology look. Combined with the engraved bridge and exposed balance, this is reminiscent of high-end complicated watches of yesterday and today. But the Hebdomas movement has always been a lower-priced offering.
Most Hebdomas watches feature the "Hebdomas" name centered in the dial and "8 Jours" engraved twice, on either side of the balance. Most also feature a flower or arrow design above this. Many also feature circular or inset numerals at all 12 positions on the dial, giving the look of a jumping hours design.
Due to its small size (15 or 19 ligne), the Hebdomas movement found its way into wristwatches quite early. Most examples are oriented with the crown at 3:00 and the exposed balance at 9:00, though some also have a "bullhead" design with the crown between the lugs at 12:00.
The 8-day movement was invented in 1888 in the Vallée de Joux in Switzerland, with the patent granted on January 10, 1889 to Iréné Aubry of Saignelégier. Initially produced under license by Arthur Graizely and his brother in La Ferrière, the watch used the names "Octava" and "Octodi". Graizely added more patents, including one for a power reserve indicator and another, dated October 9, 1901, that established the famous dial layout of the Hebdomas movement.
The novel product caught the attention of Otto Schild of Grenchen, and the two set up a joint company in La Chaux-de-Fonds known as Graizely & Co in 1901. Schild had also established a company in La Chaux-de-Fonds by 1902 and also manufactured 8-day watches using the Graizely movement. By 1906, Graizely had registered the "Hebdomas" brand name and was producing both pocket watches and wristwatches with the familiar design. His company had acquired more patents by then, including a central winding pinion and digital time display.
Schild & Co
This Graizely-Schild partnership was dissolved between 1906 and 1915, with the license passing to a new company, Schild & Co in La Chaux-de-Fonds. Production of Hebdomas watches by Schild is commonly said to have begun in 1913, though it is clear that many examples predate this. It received medals as early as 1896 in Geneva and was seen in Paris, Chicago, and Milan before 1910. It was said that the La Chaux-de-Fonds factory was producing 1000 examples per day with 1000 workers by 1918.
In 1920, Schild consolidated production of 8-day movements with the acquisition of the "Septima" brand. The company also manufactured an electric clock for automobiles known as the "Reform". Another Schild brand, "Orator", was established in 1944 and became the primary brand for these 8-day clocks. Production of the Hebdomas 8-day movement continued through the 1950s, though it was considered too large for wrist use by that time. After a short hiatus, it was re-launched by Schild in 1968 and remained in production in pocket watches until Schild entered insolvency in 1979.
Schild used many other brands in those years, including "Abyssal", "Adelco", "Air-Time", "Calendron", "Champion", "Christina", "Cortland", "Cosmos", "Cosmos-Electric", "Cristal Watch", "Cristama", "Cristina", "Dafinos", "Duchesse", "Duplex", "Eclair", "Electras", "Electrora", "Elivar", "Federate", "Fidelis", Florys", "Fullswing", "Globemaster", "Klement", "Mirax", "Perpetua", "Punktal", "Sonanto", "Starco", "Superior", "Tempus", "Texture", "Tresor", "Triumph", and "Vigor". The company was reorganized in 1986 as Fibeg SA in Bienne.
In 1982, the design, trademark, and production of Hebdomas movements was taken on by Xantia, a private-label watch company. Hebdomas would become their primary owned brand through the 1990s, with variations on the 8-day movement serving as just one of several products under that name.
As Hebdomas, Xantia also produced an interesting and unrelated model, the Baladin, based on the ETA 2824 and said to be designed by Vincent Calabrese. Hebdomas used the Ascot name on both 8-day and Valjoux 7760 chronographs, and produced a jumping hours watch that ironically used an A. Schild movement. Many of these were available in gold, with prices rising over 20,000 Euros in the 1990s.
Production of the 8-day Hebdomas movement by Xantia continued into the 1990s, with advertisements sighted in 1991.
In 2002, Europa Star reported that Kolber was the new producer of Hebdomas pocket watches. This Geneva-based company had been founded in 1983 as a producer of moderately-priced watches. Kolber's Hebdomas watches were listed at just CHF 2,000, far below Xantia's positioning, and were more of a novelty line among skeletonized models. Within a few years, Kolber appears to have moved further downmarket into the fashion watch range below CHF 1,000 and abandoned the Hebdomas line.