Astronomy

Astronomical computation layer underpinning the entire library. Provides sub-second precision solar term moments via VSOP87D with DE441 polynomial correction, lunar calendar generation from Meeus Ch. 49 new moon series, and a 5,000-year eclipse catalogue. All functions accept and return standard JS Date objects in UTC.

DeltaT (ΔT)

Export	Description
deltaT(date)	ΔT in seconds for a Date (TT = UT + ΔT)
deltaTForYear(y)	ΔT in seconds for a decimal year

Julian Day Number (儒略日)

Export	Description
julianDayNumber(year, month, day, calendar?)	JD for a calendar date (Julian, Gregorian, or auto)
jdToCalendarDate(jd, calendar?)	Convert JD back to calendar date
julianCalendarToDate(year, month, day)	Convert a Julian calendar date to a JS Date

Solar Terms (節氣)

Export	Description
SOLAR_TERM_NAMES	24 term names (小寒 through 冬至)
SOLAR_TERM_LONGITUDES	Ecliptic longitudes (285° through 270°)
findSolarTermMoment(longitude, year, startMonth?)	Exact UTC moment for a solar longitude
getSolarTermsForYear(year)	All 24 terms with exact dates
findSpringStart(year)	Exact moment of 立春
getSolarMonthExact(date)	Which solar month a date falls in

New Moon (朔日)

Export	Description
newMoonJDE(k)	JDE of new moon for lunation number k (Meeus Ch. 49)
findNewMoonsInRange(startJD, endJD)	All new moon JDEs in a Julian Day range

Lunar Calendar (農曆)

Export	Description
getLunarMonthsForYear(lunarYear)	All lunar months for a year (12 or 13)
getLunarNewYear(gregorianYear)	Lunar New Year date (正月初一)
gregorianToLunar(date)	Convert Gregorian date to lunar date

Eclipses (日月食)

Export	Description
getAllSolarEclipses()	All solar eclipses (-1999 to 3000 CE), sorted by date
getAllLunarEclipses()	All lunar eclipses (-1999 to 3000 CE), sorted by date
getEclipsesForYear(year)	All eclipses for a given year
getEclipsesInRange(start, end, kind?)	Eclipses in a date range, optionally filtered
findNearestEclipse(date, kind?)	Nearest eclipse to a given date
isEclipseDate(date)	Check if a UTC date has an eclipse
ECLIPSE_DATA_RANGE	{ min: -1999, max: 3000 }

Types

interface SolarTerm { name: string; longitude: number; date: Date; }
interface LunarMonth { monthNumber: number; isLeapMonth: boolean; startDate: Date; days: number; }
interface LunarDate { year: number; month: number; day: number; isLeapMonth: boolean; }

type EclipseKind = 'solar' | 'lunar';
type SolarEclipseType = 'T' | 'A' | 'P' | 'H';
type LunarEclipseType = 'T' | 'P' | 'N';
interface Eclipse { date: Date; kind: EclipseKind; type: SolarEclipseType | LunarEclipseType; magnitude: number; }