Chinese Calendrics Software 1.  Introduction

The Chinese Lunar Calendar is not only a lunar calendar but also a solilunar calendar (what some call a 'lunisolar' calendar), consisting of months corresponding exactly to lunar cycles and years which stay more-or-less in sync with seasonal years. Implicit in the construction of this calendar is a separate solar calendar, less well-known. Both calendars depend on the times of certain astronomical events, principally dark moons and winter solstices. For at least several centuries (according to some scholars, since the 5th C. BCE) the times of these events have been ascertained not by observation but rather by calculation, so these calendars can be classified as rule-based.

The solar calendar consists of a series of seasonal years which are divided into 24 "solar terms". The lunar calendar consists of a series of years which are divided into 12 or 13 lunar months. A solar year always begins at the (northern) winter solstice, on or around December 21st in the Common Era Calendar. A lunar month always begins on the day of a dark moon. The beginning of a lunar year (i.e, lunar new year's day) is more difficult to define (it is defined in Section 4 of the user manual for this software); it always occurs from about January 20th to about February 20th, i.e., about a month or so after the start of the solar year.

Note that Chinese Calendrics uses the astronomical year numbering system for years in the Julian and Common Era (a.k.a. Gregorian) Calendars.

Next: Dark moon, lunation, equinox, solstice
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