Solstice & Lunistice Calendar

Why 18.6 years?
The Moon's orbital plane is inclined approximately 5.15° to the ecliptic plane. The lunar nodes (the points where the orbit intersects the ecliptic) complete one full revolution along the ecliptic in approximately 18.6 years. When the nodes are positioned so that the Moon's inclination adds to the Sun's ecliptic obliquity (major standstill), the Moon can reach ±28.5° declination. When the nodes are in the opposite position (minor standstill), the Moon reaches only ±18.3° declination.

Megalithic connection:
The lunistice cycle is one of the oldest known astronomical observations in human history. Stonehenge, the Callanish Stones and other megalithic structures are thought to have been aligned to mark the Moon's extreme rising and setting points. Irish archaeologist Alexander Thom documented the lunistice alignments of hundreds of megalithic sites across the British Isles.

Astrological significance:
During major standstill years, the lunar nodes are near the Aries-Libra or Cancer-Capricorn axis. In these periods, eclipses have more dramatic effects because the Moon can deviate further from the ecliptic and the shadow geometry changes. In classical astrology, the nodal sign transits are fundamental indicators of mundane astrology.

What is a Solstice?
A solstice is the moment when the Sun reaches its northernmost or southernmost declination on the ecliptic. At the summer solstice (around June 21), the Sun reaches +23.44° declination, producing the longest day in the northern hemisphere. At the winter solstice (around December 21), the Sun descends to −23.44° declination. The word comes from Latin "sol" (sun) and "sistere" (to stand still): the moment when the Sun's north-south movement stops and reverses direction.

What is an Equinox?
An equinox is the moment when the Sun crosses the celestial equator, making day and night approximately equal in length. The vernal equinox (around March 20) marks the Sun's passage into the northern celestial hemisphere, while the autumnal equinox (around September 22) marks its passage into the southern hemisphere. Astrologically, the vernal equinox defines the starting point of the tropical zodiac at Aries 0°.

What is a Lunistice (Lunar Standstill)?
The term lunistice is derived from Latin "luna" (moon) and "sistere" (to stand still), and is the lunar counterpart of the solstice. It refers to the moment when the Moon's declination reaches its most extreme value and reverses direction. The Moon reaches its northern and southern declination extremes approximately every 27.3 days. However, the magnitude of these extremes varies on an 18.6-year cycle.

Major Standstill:
When the lunar nodes are positioned on the ecliptic such that the Moon's orbital inclination (5.15°) adds to the Sun's ecliptic obliquity (23.44°), the Moon can reach ±28.6° declination. In these years, the Moon rises higher in the sky than the Sun ever can, and sets lower than the Sun ever does. Last major standstill: 2025. Next: 2043.

Minor Standstill:
When the nodes are in the opposite position, the Moon's orbital inclination is subtracted from the Sun's ecliptic obliquity. The Moon can only reach ±18.3° declination, meaning it cannot even reach the height that the Sun achieves. Last minor standstill: 2015. Next: 2034.

Calculation method:
Solstice and equinox dates have been calculated using the astronomy-engine library's Seasons function. Lunistice data was obtained by sampling Moon declination at 3-day intervals throughout each year and then determining local maximum/minimum points using golden section search. All times are in UTC.