JODIAC · GUIDE
Quick guide
Jodiac converts a Gregorian (solar) date to four calendar layers: the lunar (Chinese) calendar, the Chinese zodiac animal, the Western sun-sign and the 24 solar terms. Below is a plain-language primer.
1. Chinese zodiac — the lunar-new-year rule
Each year is tagged with one of 12 animals (Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Goat, Monkey, Rooster, Dog, Pig). The animal flips on lunar new year — usually late January or early-to-mid February — NOT on January 1. Jodiac handles the edge by converting to the lunar year first.
2. Lunar calendar
The East Asian lunar calendar has 12 or 13 months, each 29 or 30 days long. About every 2-3 years a leap month is inserted to stay synchronised with the seasons. Our data table covers 1900-01-31 through 2100-12-31.
3. Western horoscope
Based purely on Gregorian month + day. Cut-offs follow the traditional tropical-zodiac table used by most astrology publications.
4. 24 solar terms (節氣)
The year is split into 24 equal solar-ecliptic segments such as Lichun 立春 (Start of Spring) and Dongzhi 冬至 (Winter Solstice). Knowing which term your birthday belongs to is traditional trivia in Korea, China and Japan.
5. Korean age systems
Korea historically used three parallel age counts. Jodiac shows all three: Korean age (세는 나이) counts you as 1 at birth and adds a year each Seollal; international age (만 나이) is what most of the world uses; legal-year age (연 나이) is used in selected laws — conscription, school enrolment, youth-protection statutes.