# Syna personal readings

Four readings share a birth-details form under Your readings. Calculations and original interpretation rules run locally in a Web Worker. Names, birth dates, times, coordinates, and results are not sent to a reading service or language model and are not automatically stored. Only typed city searches go to Open-Meteo / GeoNames; manual coordinates are available.

## Zodiac profile

Sun and Moon signs come from apparent geocentric tropical ecliptic longitudes, using Astronomy Engine 2.1.19. Rising is calculated from the birth instant and location. The reading combines original, contextual prose for the sign with the planet's traditional theme. Fire/Earth/Air/Water and cardinal/fixed/mutable labels describe traditional groupings, not measurements of a person. No hard-coded date ranges substitute for the Sun calculation.

## Full birth chart

All ten planets (Sun through Pluto), their signs and degrees, whole-sign house placements, the ascendant and midheaven, and twelve house cusps are included when the time is known. Each unordered pair of planets is compared once. Aspects are conjunction (0°), sextile (60°), square (90°), trine (120°), and opposition (180°), with 6° orbs except 4° for sextiles. They are sorted by orb divided by allowed orb. These thresholds are editorial choices. The prose names the actual planets, signs, houses, and detected aspects that select it; no compatibility percentage or personality score is invented. Slow outer-planet placements are identified as generational.

Unknown birth times use local noon only as a display reference, with hourly samples across the entire civil birth day plus its final instant. A sign changing during that day is labelled unresolved. Stable Sun/Moon signs can have sign-only interpretations, explicitly shown with birth-time uncertainty; no Moon aspects, rising, or houses are supplied. Other aspects must remain within the conservative uncertainty bounds from the shared chart engine. Birth-time and time-zone validation is shared with Compatibility and Your forecast.

## Chinese zodiac

This is a birth-year animal, element, and yin/yang reading. It uses the browser's Intl Chinese calendar (ICU data), with the Lunar New Year boundary. The entered local civil date is evaluated as a date, without shifting it into another location. The related Gregorian year identifies the sexagenary cycle, anchored to Jia-Zi / Wood Rat in 1984. Twelve earthly branches map to Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Goat, Monkey, Rooster, Dog, and Pig. Ten stems map in pairs to Wood, Fire, Earth, Metal, and Water, alternating yang and yin. January/February birthdays can belong to the preceding animal year. Unsupported Chinese-calendar runtimes produce an error, not a Gregorian-year guess.

This explicitly uses the popular Lunar New Year convention. It is not a Four Pillars / BaZi chart; traditions using the Start of Spring (Li Chun) boundary can give a different year pillar. Interpretations are original reflections on conventional symbolism, not copied source text or factual character assessments. Only a name (optional) and birth date are required for this mode.

## Birthday / solar-return reading

A known birth time is required. The script finds the instant when the Sun returns to its natal apparent tropical longitude near the selected birthday year. A ±10-day bracket handles leap-day birthdays and longitude wraparound; bisection narrows it to one second. Both endpoints use the same astronomy calculation as the natal Sun. The numerical search tolerance is not an ephemeris accuracy claim: Astronomy Engine targets approximately one arcminute, and the birth record can be less precise.

The ten return positions, internal major aspects, and whole-sign houses are calculated at that instant. The selected return location sets its angles and houses, defaulting visibly to the birthplace; users can choose another city or manual coordinates. The Sun's return house leads the reflection, followed by the return Sun/Moon/rising and the other planetary themes. Its period ends at the following solar return. This is a return-chart interpretation, distinct from the January–December transit forecast. It does not claim to predict events or time them to arbitrary months.

## Sources and scope

- Astronomy Engine documentation and source: https://github.com/cosinekitty/astronomy/tree/master/source/js
- Temporal time-zone handling: https://tc39.es/proposal-temporal/docs/zoneddatetime.html
- Astrodienst chart calculation terminology: https://www.astro.com/faq/fq_fh_calc_e.htm
- Astrodienst major aspects: https://www.astro.com/astrowiki/en/Aspect
- Astrodienst solar-return definition and location conventions: https://www.astro.com/astrowiki/en/Solar
- Hong Kong Observatory animal cycle: https://www.hko.gov.hk/en/gts/time/12animals.htm
- Hong Kong Observatory stem/branch cycle: https://www.hko.gov.hk/en/gts/time/stemsandbranches.htm
- Smithsonian overview of the animal and element cycle: https://www.si.edu/spotlight/year-of-the-dragon
- Hong Kong Observatory Gregorian/lunar conversion tables (boundary fixtures): https://www.hko.gov.hk/en/gts/time/conversion.htm
- Geocoding: https://open-meteo.com/en/docs/geocoding-api and https://www.geonames.org/

Astrology is not a scientifically validated personality assessment or forecast. These readings are reflection prompts, not diagnostic, financial, health, or relationship predictions. The four readings are deterministic for the same inputs and runtime calendar/time-zone data. The full suite checks shared planetary positions against independent Swiss Ephemeris fixtures, plus Lunar New Year boundaries, unique aspects, uncertainty exclusions, solar-return longitude/root bounds, year changes, relocation, invalid inputs, and leap dates.