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Zodiac Sign Calculator

Looks up the tropical Western sun sign (with its conventional date range and a cusp flag) and the Chinese zodiac animal, heavenly-stem element and yin/yang polarity for a birth date, using the actual Chinese New Year dates from 1924 to 2044 so January and February births are assigned to the correct lunar year.

When to use

You need someone's star sign, whether they were born on a cusp, or their Chinese zodiac animal and element (e.g. Metal Horse) from a date of birth.

Do not use when: You need a full natal chart (moon or rising sign, which depend on time and place of birth) or the exact minute the Sun changed sign in a given year; for ages and birthdays use age.

Formula

sun_sign: tropical sign whose conventional date range contains (month, day): Aries 21 Mar–19 Apr, Taurus 20 Apr–20 May, Gemini 21 May–20 Jun, Cancer 21 Jun–22 Jul, Leo 23 Jul–22 Aug, Virgo 23 Aug–22 Sep, Libra 23 Sep–22 Oct, Scorpio 23 Oct–21 Nov, Sagittarius 22 Nov–21 Dec, Capricorn 22 Dec–19 Jan, Aquarius 20 Jan–18 Feb, Pisces 19 Feb–20 Mar. Chinese: lunar_year = year if birth_date ≥ Chinese New Year of that year, else year − 1; animal = (Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Goat, Monkey, Rooster, Dog, Pig)[(lunar_year − 1924) mod 12]; element = (Wood, Fire, Earth, Metal, Water)[floor(((lunar_year − 1924) mod 10) / 2)]; polarity = Yang if lunar_year is even else Yin

Western sign boundaries use the common calendar convention; the Sun's actual ingress varies by about a day from year to year, so dates within one day of a boundary are flagged as cusp. Chinese New Year dates 1924–2044 are taken from the Hong Kong Observatory lunar-calendar tables; 1924 (Jia-Zi, Wood Rat) starts the current sexagenary cycle.

Inputs

Parameter	Type	Unit	Required	Description
`birth_date`	date		yes	Date of birth (ISO 8601, YYYY-MM-DD). Chinese zodiac is available for dates from 1924-02-05 to 2044-01-29.

Outputs

Output	Type	Description
`sun_sign`	string	Tropical zodiac sign by calendar date.
`sun_sign_dates`	string	Conventional date range of the sign (boundaries can shift by a day between years).
`sun_sign_element`	string	Classical element of the sign: fire, earth, air or water.
`on_cusp`	boolean	true when the birthday is within one day of a sign boundary, so the real sign depends on the year and time of birth.
`chinese_animal`	string	One of the 12 earthly-branch animals (Rat … Pig) for the lunar year of birth.
`chinese_element`	string	Heavenly-stem element of the lunar year: Wood, Fire, Earth, Metal or Water (each covers two consecutive years).
`yin_yang`	string	Yang for even lunar years, Yin for odd lunar years.
`chinese_zodiac`	string	Combined label, e.g. 'Yang Metal Horse'.
`lunar_year`	integer	Chinese lunar year the birth falls in (Gregorian year of its New Year).
`chinese_year_start`	date	Chinese New Year that began the birth year.
`chinese_year_end`	date	Day before the next Chinese New Year.

Example

Born 1990-05-17: {"birth_date":"1990-05-17"} → {"sun_sign":"Taurus","sun_sign_dates":"April 20 – May 20","sun_sign_element":"earth","on_cusp":false,"chinese_animal":"Horse","chinese_element":"Metal","yin_yang":"Yang","chinese_zodiac":"Yang Metal Horse","lunar_year":1990,"chinese_year_start":"1990-01-27","chinese_year_end":"1991-02-14"}

Born 2000-01-15 (before Chinese New Year 2000-02-05): {"birth_date":"2000-01-15"} → {"sun_sign":"Capricorn","on_cusp":false,"chinese_animal":"Rabbit","chinese_element":"Earth","yin_yang":"Yin","chinese_zodiac":"Yin Earth Rabbit","lunar_year":1999,"chinese_year_start":"1999-02-16","chinese_year_end":"2000-02-04"}

GET https://tttkmbb.com/api/v1/calculate/zodiac?birth_date=1990-05-17

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/zodiac (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/zodiac · Markdown: https://tttkmbb.com/everyday/zodiac.md · JSON definition: https://tttkmbb.com/everyday/zodiac.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="zodiac"
OpenAPI operationId: classify_zodiac_signs
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

Hong Kong Observatory – Gregorian-Lunar Calendar Conversion Table (government)
Chinese zodiac – table of years with Gregorian start and end dates, 1924–2043 (Wikipedia) (reference)
Astrological sign – tropical sun-sign dates (Wikipedia) (reference)

FAQ

Why does a January or February birthday get the previous year's animal?

The Chinese zodiac follows the lunisolar year, which starts on Chinese New Year (between 21 January and 20 February). Someone born on 15 January 2000 was born in the lunar year 1999, the Earth Rabbit, not the Metal Dragon.

What does 'on a cusp' mean?

The Sun enters each sign at a specific moment that shifts by about a day from year to year, so a birth within a day of the conventional boundary could belong to either sign; an ephemeris for the birth year and time settles it.

Is the Chinese element the same as the animal's fixed element?

No. This calculator reports the heavenly-stem element of the year (changes every two years); each animal also has a fixed branch element (e.g. Horse is fire) used in some traditions.

Related calculators

Age Calculator — Exact age and next birthday from the same date of birth.
Day of the Week Calculator — Weekday of the birth date.