How the dates are read and the signs found

Every tool and page reads one data set: the lunar months and solar terms from 1901 to 2100, taken from the Hong Kong Observatory's Gregorian-Lunar Calendar Conversion Tables and read on November 1, 2026. No date is typed into a page; each one is computed from that data when the site is built, and the tools compute the same way in your browser.

1. Reading the tables

The Observatory publishes one text file per year, with a line for each day: the Gregorian date, the lunar day, the start of each lunar month, the weekday and the solar term that falls that day. A script reads the 200 files and keeps the first day of each lunar month with its number, 200 lunar new years and the 24 solar terms of each year. A month that repeats the number of the month before is a leap month: 73 of them between 1901 and 2100.

2. Checks

• every lunar month has 29 or 30 days;
• every Gregorian year has its 24 solar terms, in order;
• the stem, branch and animal printed in the title of each yearly file match the ones computed from the year, for every year from 1902 to 2100;
• automated tests check known dates, such as the new years of 2026 and 2027, the leap months of 2023 and 2025, and the boundaries of January and February signs.

3. From a date to a sign

Under the usual rule, a date belongs to the lunar year whose new year is the latest one on or before it; the animal comes from the branch and the element from the stem, following the Observatory's table of the sixty names. Under the Spring Commences rule of Four Pillars charts, the year starts at that solar term instead. Both are offered; the default is the lunar new year, which the Observatory itself uses to change the year name. The tools work with dates, not hours: on the day of a change, the hour of birth can matter under the solar rule.

4. Range

The tools accept dates from January 1, 1901 to December 31, 2100, the range of the tables. A date outside it gets no answer rather than a guess. Lunar year 1900, which covers January 1901 up to the new year of February 19, 1901, is named but its start date is not in the tables.

5. Traditions

The pairings of signs, triads, harmonies, clashes and harms, are computed from the positions of the branches as tradition defines them. The traits of the animals are written as descriptions of folklore. Neither is presented as a fact about any person, and the site makes no prediction.

6. Pages and tables read

Method version of November 1, 2026. A date that looks wrong: contact.