Lunar Structure

Lunar Structure (M0–M14)

The Light Calendar uses a simple lunar index. Each lunar cycle has a home year: the Light Year in which its full moon occurs.

The “normal” moons of a Light Year are numbered M1–M13. In addition, there can be an M0 (and in rare cases an M14) to show spill-over cycles at the year boundaries.

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Basic Rules

• Home-year numbering: M1–M13
  • A lunar cycle belongs to the Light Year in which its full moon occurs.
• Start of a lunar cycle:
  • The cycle starts at the astronomical new moon, rounded by a natural rule:
    • New moon before 12:00 UTC → previous night (start date = previous day)
    • New moon at/after 12:00 UTC → same day
• Cycle length is 29 or 30 days.

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Edge Moon: M0 (and possible M14)

To avoid gaps at the Light Year boundary, neighbouring cycles are still shown:

• M0

  • Represents the last moon of the previous Light Year, whose cycle still extends into the first days of the new year.
  • Its full moon lies before the Solar New Year (before 1 New February), but its tail is still visible in the new year, so it is displayed as M0·x.

• M14 (very rare)

  • In some years, a first moon of the next Light Year can already start in the last days of the current year.
  • In that case, the implementation may display it as M14·x as a forward spill-over.
  • Conceptually, you can still think in terms of M0–M13; M14 is just a rare edge case.

In practice, this ensures that every date shows a moon index (even on the first and last days of the year), and no cycle is visually “cut off”.

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Example Notation

Μ11·19(16/30)

Meaning:

• Μ11 → 11th moon of the Light Year
• 19 → today is day 19 of this lunar cycle
• 16 → the full moon occurred on day 16 of this cycle
• 30 → total length of this cycle (29 or 30 days)

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Purpose

The lunar index (M1–M13, plus edge moons M0 and rarely M14) provides full lunar orientation without a separate lunar calendar, while remaining astronomically precise and continuous at year boundaries.