Geared Lunarium – 19-Year Metonic Moon Calendar

🌙⚙️ Metonic Lunarium — A Gear-Driven Perpetual Moon Phase Dial ⚙️🌙

This lunarium is a hand-crank mechanical moon phase display built on real astronomy, not guesswork. At its core is a 19:1 gear train ⚙️ that replicates the Metonic cycle 🔭 — the 2,400-year-old discovery that 19 solar years and 235 lunar months line up almost perfectly. Turn the gear, and the moon phase sphere 🌗 rotates through its cycle while the month ring 📅 and year ring advance together, always staying in sync with the real sky ✨.

⚙️ How it works

• A compound gear train (120T and 160T concentric rings, stepped down through smaller pinions) converts full rotations into a precise 19:1 ratio
• The outer year ring carries 10 pre-calculated reference years 🗓️ (1938, 1957, 1976, 1995, 2014, 2033, 2052, 2071, 2090, 2109) — each one a real, ephemeris-confirmed New Moon 🌑 closest to January 1 of that year
• Set the dial to whichever reference year is closest to today, and the mechanism stays accurate to within hours for the next two decades — recalibrate to the next reference year on the ring, and it holds that accuracy indefinitely ♾️
• The inner sphere shows the current moon phase 🌓; the two rotating markers track the month and the "years passed" since your reference point

🎯 Why it's accurate

Most novelty moon dials drift out of sync within a few years because they ignore the small mismatch between the solar year and the lunar month. This one is built around that mismatch directly — the reference-year system resets the error to near-zero every 19 years, so the gear train never has to carry more than a few hours of drift at a time ⏱️.

A functional piece of astronomical engineering as much as a desk display 🖥️ — equal parts orrery 🪐, calendar 📆, and conversation piece 💬.