A recent study published in Palaeohispanica has uncovered compelling evidence of advanced timekeeping among the Celts. The research, conducted by Professor Roberto Matesanz Gascón from the University of Valladolid, focuses on an intricately designed gold artifact known as the lunula from the Chão de Lamas treasure in Portugal. His findings suggest that this piece of jewelry may have played a crucial role in synchronizing lunar and solar cycles within the Celtic calendar.

A New Interpretation of the Chão de Lamas Lunula

Traditionally regarded as a decorative ornament, the lunula—shaped like a crescent moon and found in Chão de Lamas (Miranda do Corvo, Coimbra)—has now been reanalyzed. Matesanz’s study reveals that its complex geometric design likely represents a sophisticated Celtic calendrical system spanning 114 years. This period aligns with six Metonic cycles, each lasting 19 years, a well-documented astronomical method used to reconcile the lunar and solar calendars.

Linking the Lunula to the Coligny Calendar

The Coligny calendar, discovered in France and dating to the 2nd century AD, provides extensive insights into how the Celts measured time. Structured into five-year cycles with 62 months, it totals 1,835 days. However, scholars have long debated how this system aligned with the solar year of 365.24 days.

Matesanz’s research establishes a connection between the Coligny calendar and the lunula’s geometric motifs. He proposes that the artifact's circular patterns represent a method for adjusting the solar year by eliminating 53 days every 114 years. Interestingly, the number 53 also appears in Irish literary sources, hinting at a broader Celtic tradition that spanned regions.

Geometric Patterns and Celestial Calculations

The lunula’s design consists of large concentric circles and smaller circles with central dots, organized into five distinct sections. Matesanz theorizes that these elements correlate with the months within the Celtic five-year cycle.

Significantly, the study suggests that the lunula symbolizes six of these cycles, amounting to 30 years—a timeframe identified by Pliny the Elder as the Celtic saeculum. However, this calculation results in an excess of 53 days compared to the solar cycle. To correct this discrepancy, the Celts may have periodically omitted these days every 114 years, ensuring their festivals and seasonal observations remained in sync with celestial changes.

Connections to Irish Mythology

One of the most intriguing aspects of this research is the link between the 53-day adjustment period and Irish mythology. In the medieval tale Baile in Scáil, the legendary king Conn Cétchathach encounters a mystical stone on the Hill of Tara, where druids claim they cannot reveal his name until 53 days have passed. This period of silence may correspond to the time correction in the Celtic calendar, suggesting that ancient timekeeping methods persisted through oral traditions long after Roman influence.

Art as a Timekeeping Tool

Matesanz’s study challenges traditional views of Celtic art, proposing that symbols and designs held deeper mathematical and astronomical meanings. The Chão de Lamas lunula may exemplify how the Celts encoded timekeeping knowledge into their artistic expressions.

Additional archaeological discoveries support this idea. In the Iberian Peninsula, objects like the Axtroki bowls and the Leiro helmet feature iconography that may have calendrical significance. Similarly, Central European artifacts such as the Schifferstadt-type golden hats have been interpreted as time-measuring instruments, reinforcing the notion of a shared understanding of time across ancient cultures.

Conclusion

If validated, this research could revolutionize our understanding of Celtic astronomy and timekeeping. It suggests that the Celts possessed a sophisticated grasp of lunar and solar cycles, reflected in both their artifacts and mythology. The Chão de Lamas lunula, once seen merely as an ornament, may instead be a key to unlocking the secrets of how the Celts measured and understood time.