The Sixth Day of the Moon

Among the few ancient voices that whisper to us about the Druids, Pliny the Elder stands out. In Naturalis Historia (Book 16), he records a curious detail, the Druids chose the sixth day of the Moon to gather their most sacred plant. Why this day? Why not the full moon or the new? And what does this reveal about the Gaulish understanding of time?

This single note is more than a curiosity—it is a key that unlocks the logic of the Coligny Calendar, the cycles of Samos and Giamos, and the deeply liminal mindset of the ancient Gauls.

Pliny writes:

“…ante omnia sexta luna, quae principia mensum annorumque his facit et saeculi post tricesimum annum, quia iam virium abunde habeat nec sit sui dimidia…”
(Pliny, NH 16.250)

Translation:
“…above all, on the sixth moon, which makes the beginnings of their months and years, and of their thirty-year cycle; because it already has strength in abundance, but is not yet halfway through its course…”

Counting the Moon

Pliny clearly says sixth moon, yet some modern sources speak of the fifth day. Why? Ancient cultures often counted the first day as “day one,” so their sixth day might correspond to our fifth day after the new moon. The Gauls likely began their month not at the invisible astronomical new moon, but when the first crescent appeared, 1–2 nights later.

So when Pliny says “sixth day,” he means the sixth day after first visibility—a strong waxing crescent, just before first quarter.

Ancient observers often reckoned lunar days from first visible crescent (not the invisible astronomical new Moon). Counting inclusively, the “6th day” falls when the Moon is approaching first quarter—the first cleanly visible shape that anyone looking up can identify with confidence. That makes it a practical anchor for communal ritual timing and for beginning a new lunation in a pre-telescope culture. Scholarly reconstructions of the Coligny system lean on this logic: start counting the month when the Moon is visibly strong but not yet half—exactly the reasoning Pliny attributes to the Druids.

Julius Caesar confirms this cultural pattern in De Bello Gallico (6.18):

“They count the passage of time by nights, not by days. Birthdays and the beginnings of months and years, all these they observe as starting from the night.”

The Gauls began everything in darkness, letting light follow. This worldview harmonizes with a lunar system anchored in visibility and strength. If time begins at night, then the sixth night after first visibility becomes a powerful threshold. A phase where the Moon is no longer faint, yet not fully balanced, ideal for rites of renewal, healing, and cosmic alignment.

Why the Sixth Day?

Pliny gives this reason:

“…because it already has abundant strength, but is not yet half.”

This day sits at a threshold. The Moon has emerged from darkness and weakness. It is waxing toward fullness, rich with growing power. But it is not yet in perfect balance (first quarter) nor at its peak (full moon).

This liminal moment embodies potential, growth, and potency—perfect for healing rites and the gathering of sacred herbs.

The Coligny Connection

The Coligny Calendar, the great bronze tablet from Gaul, divides the month into two halves:

SAMOS (bright) — waxing Moon and first half of the cycle.
GIAMOS (dark) — waning Moon and second half.

Many scholars (Lambert, Duval & Pinault, McKay) argue that Day 1 of each month corresponded to this bright surge of light—near the sixth day, where Pliny locates his ritual. From this point, the Coligny months flow naturally into the waxing strength of SAMOS and the inward-turning hush of GIAMOS.

“While Pliny emphasizes the sixth day, many modern reconstructions set First Quarter as the clear marker for the beginning of Samos, and Last Quarter as the start of Giamos, dividing the month into bright and dark halves.”

From our modern perspective, time is often imagined as a line: fixed beginnings and endings, rigid boundaries between months and years. The Gauls, however, seem to have embraced something far more fluid. Caesar’s and Pliny’s notes, and the Coligny calendar itself, hint at a worldview where cycles, not lines, defined existence. In such a view, Samos and Giamos were not walls but tides—bright and dark, each melting into the other. The sixth day, the first quarter, even the turning of the year were liminal thresholds, not absolute doors. Everything was always becoming, never static.

This fluid sense of time reflects the heart of Gaulish cosmology, transformation, continuity, and interconnection. Day flows into night, life into death, dark into light—and back again, without rupture. To live by these rhythms is to embrace a world where nothing truly ends, only changes shape. As we see with how they viewed death.

A Marker of Larger Cycles

Pliny does not stop at months. His words are explicit:

“…ante omnia sexta luna, quae principia mensum annorumque his facit et saeculi post tricesimum annum…”
“…above all, on the sixth moon, which makes the beginnings of their months and years, and of their thirty-year cycle…”

The sixth day of the Moon was not merely a monthly rhythm. It likely served as the cosmic hinge for greater cycles—the year itself and the long 30-year ritual cycle (saeculum). What does this mean? That the Gaulish world flowed from a single lunar anchor point. Months, years, even generations echoed the same sacred pattern, a brightening Moon before balance, a time of potential rising toward fullness. If the Coligny calendar reflects this, the first month of the year may have begun at a waxing Moon near the spring equinox, with the sixth day marking the formal turn into Samos, the bright half of the year. This insight shows a truth about Gaulish cosmology (in my opinion) beginnings were never arbitrary—they were tied to the visible, growing, living power of the Moon.

The sixth day of the Moon is more than a technical detail from Pliny—it is a glimpse into a world that moved in cycles, not straight lines. It shows us a time when beginnings were thresholds, not walls; when every moment flowed into the next like tides of darkness and light. To the Gauls, the waxing Moon was not just a phase—it was a promise: strength gathering, life expanding, the world leaning toward fullness. To honor this rhythm was to align with the heartbeat of the cosmos itself. Perhaps that is why they called their sacred mistletoe “all-healing”. It was not the plant alone that healed, but the harmony between time, ritual, and living nature. A wisdom we can reclaim today—not by fixing time on a calendar, but by feeling it rise and fade in the sky above us, and in the flow of our own becoming.

Ritual Guide for the Lunar Cycle (Gaulish Context)

Shows the lunar phases, Pliny’s sixth day, and how SAMOS and GIAMOS align.

Phase	Gaulish Context	Ritual Themes
Day 1 (First Crescent)	Emergence, omens	Divination, new prayers
Day 6 (Pliny’s Day)	Threshold before Samos	Healing, sacred herb gathering
First Quarter	Start of SAMOS (Bright)	Oaths, blessings, expansive energy
Full Moon	Culmination	Major offerings, communal rites
Last Quarter	Start of GIAMOS (Dark)	Release, balance, inward focus
Dark Moon	Deep Giamos	Silence, incubation, renewal

Gaulish Words for the Moon Phases

SAMOS (Bright Half):

Macarnolugrâ — Growing Moon (First Quarter)
Leucolugrâ — Bright Moon (Full Moon)

GIAMOS (Dark Half):

Maruolugrâ — Dying Moon (Last Quarter)
Dubulugrâ — Dark Moon (New Moon)

Note
Other interpretations exist regarding when the Gaulish calendar begins and ends, and each theory has its reasoning. The reconstruction presented above is, in my view, the most logical based on the sources we have. Ultimately, we may never know every detail with certainty. What matters most is not rigid accuracy, but connection—living in harmony with the flow of the cosmos, as the ancients once did.