Chinese calendar: convert a date to the lunar calendar

Months, leap months and days

A lunar month begins on the day of the new moon, as the Observatory puts it, when the moon and the sun reach the same longitude on the ecliptic. Months are numbered from one to twelve, and a leap month takes the number of the month before it. The converter shows it as, for example, "day 3 of the leap 6th month". Days are simply counted from 1 to 29 or 30. The first day of the first month is the lunar new year, and the fifteenth, the first full moon, is the Lantern Festival.

The 24 solar terms

The solar terms divide the sun's yearly path into 24 equal steps. Twelve are major terms, starting with the vernal equinox at 0 degrees, and twelve are minor terms between them. The Observatory's English names are kept here: Spring Commences, Insects Waken, Vernal Equinox, Bright and Clear, Corn Rain and so on. The terms fall on nearly the same Gregorian dates each year, Spring Commences on February 3, 4 or 5, the winter solstice between December 21 and 23, because they follow the sun as the Gregorian calendar does.

Leap months from 2020 to 2040

The tables give these leap months. Each one makes its lunar year thirteen months long, about 384 days.

Years: the stem-branch cycle

Years are named by pairing one of 10 heavenly stems with one of 12 earthly branches, which gives a cycle of 60 names that started again with Jia-Zi in 1984 and will restart in 2044. The branch gives the animal and the stem the element; the elements page has the full cycle. The year name changes at the lunar new year, which is the date the table of new year dates lists for every year.

The limits of the converter

It covers January 1, 1901 to December 31, 2100, the range of the Observatory's tables, and gives dates, not times: a solar term falls at an exact minute, which matters to astrologers but not to the calendar date. Dates are those of the Chinese calendar as the Observatory publishes them; nothing is recomputed here.