The Secret Calendar
OF THE PRIORY OF SION

This interactive tool reconstructs the esoteric calendar described in The Cutting of the Orm by Tracy R. Twyman (2002), which proposes that the Priory of Sion employed a hidden calendrical system encoded within the mystery of Rennes-le-Château.

The calendar divides the year into 13 months of 28 days — 364 days, or exactly 52 weeks — each month governed by one of 13 zodiac houses (including Ophiuchus, the Serpent Bearer), arranged in the order of Le Serpent Rouge.

At its heart is the Compass of Enoch: the 26 letters of the alphabet arranged on a circle, split at M and mirrored (A–M = 1–13, Z–N = 14–26). A 13-pointed star inscribed within this compass generates cipher layers — Atbash, Star Spoke, and Compass Values — that can be chained for multi-pass encoding.

Use the tabs above to explore the zodiac wheel, browse the 13-month calendar grid, convert dates between Gregorian and Priory reckoning (plus Hebrew, Julian, and Mayan calendars), examine the sacred numerology, or encode messages with the cipher tool.

The Secret Calendar

of the Priory of Sion
XIII Months · XXVIII Days · CCCLXIV Days · LII Weeks

Each month begins on Sunday and contains exactly 4 weeks (28 days). Gregorian dates shown assume Day 1 = January 1 (a working convention—the book does not specify when the Priory year begins).

The Compass of Enoch · XIII Houses of the Zodiac

Hover over a house to explore
The serpent zigzags between paired letters of the Compass of Enoch.
Click any segment for full correspondences

Note: The book does not specify when the Priory year begins relative to the Gregorian calendar. This converter currently keys Day 1 to January 1 as a working assumption. The 364-day calendar describes an idealized year from a “Golden Age” — the true anchor date, if any, remains one of the mysteries.

Gregorian → Priory Calendar

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Priory Calendar → Gregorian

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The Priory of Sion Numbers & the 364-Day Calendar

All membership numbers, when reduced by 13 and divided by 9, reveal the calendar's structure.

POS # # of 364-Day Years # of Leap Days Added # of 28-Day Months Relationships
72921 (728 + 1 = 729)26364 + 243 + 121 + 1
9 × 81
109331 (1092 + 1 = 1093)39729 + 364
218763 (2184 + 3 = 2187)78(1093 × 2) + 1
6561189 (6552 + 9 = 6561)2343 × 2187
98412713 (9828 + 13 = 9841)3516561 + 2187 + 729 + 243 + 81 + 27 + 9 + 3 + 1
29523813910539841 × 3
88569243117315929523 × 3
26570772935194779841 × 27
79712121871053284319841 × 81
239136365613159852939841 × 243

Key Correspondences

Solar Number

9

Stability in change
The Sun · The Vortex
9 planets · 9 grades

Lunar Number

13

Highest feminine unity
The Moon · Luna
13 months · 13 houses

Union

22

9 + 13 = 22
Hebrew letters
Rennes-le-Château

The Perfect Year

364

13 × 28 = 364
52 weeks exactly
364 / 13 = 28

The Compass of Enoch Cipher

The alphabet, arranged upon the Compass of Enoch, is split at M and mirrored —
A,B,C,D,E,F,G,H,I,J,K,L,M,Z,Y,X,W,V,U,T,S,R,Q,P,O,N

Plain
Value
Cipher Mode

Letter → compass position number

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How the Cipher Works

The Compass of Enoch arranges the 26 letters around a circle, split at M (13) with the second half reversed: A–M = 1–13, then Z–N = 14–26. Three geometric operations on this circle produce three cipher layers, which can be combined for deeper encoding.

Layer I · Compass Values

The simplest transformation: each letter is replaced by its position number on the compass circle. A = 1, B = 2 … M = 13, Z = 14, Y = 15 … N = 26. Words are separated by dashes, letters within a word by dots. To decode, convert each number back to its letter.

Example: SION → 21.9.25.26

Layer II · Atbash Mirror

Each letter is substituted with the letter diametrically opposite on the compass — exactly 13 positions away. A↔Z, B↔Y, C↔X … M↔N. Every line connecting an Atbash pair passes through (or very near) the centre of the circle. Because each swap is its own inverse, encoding twice returns the original text — an involution.

Example: SION → HRLM

Layer III · Star Spoke

The 13-pointed star inscribed in the compass connects each letter to a near-opposite letter. Because 13 is odd, no spoke passes through the exact centre — each one misses by half a segment. Letters at odd compass positions shift +11; letters at even positions shift +15. This creates 13 spoke pairs: A↔L, B↔W, C↔Z, D↔U, E↔X, F↔S, G↔V, H↔Q, I↔T, J↔O, K↔R, M↔P, and N↔Y. Like Atbash, the Star Spoke cipher is self-reversing.

Example: SION → FTJY

Modes IV–VI · Multi-Layer Pipelines

The three layers can be chained in sequence for progressively deeper encoding. Each mode applies its transforms left to right; decoding reverses the order.

IV · Atbash + Compass:  First substitute each letter via Atbash, then convert the result to compass numbers. Decode: numbers → letters → Atbash.

V · Spoke + Compass:  First substitute via Star Spoke, then convert to compass numbers. Decode: numbers → letters → Spoke.

VI · Three-Layer:  The deepest encoding: Atbash → Star Spoke → Compass numbers. Three passes of transformation make the output far harder to reverse by hand. Decode: numbers → letters → Spoke → Atbash.

Atbash Pairs

Star Spoke Pairs