Chinese Calendrics Software
1.  Introduction

As mentioned elsewhere, the lunar calendars used in Vietnam and Japan are the same as the lunar calendar used in China except that (a) the reference longitude differs by 15° and (b) the sets of 12 animals differ slightly. Thus everything said in this user manual about the Chinese Calendar also applies to the Vietnamese and Japanese Calendars, except where noted.

The Chinese Lunar Calendar is not only a lunar calendar but also a solilunar calendar (more usually called 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 (but the rules are not simple).

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.

The Archetypes Calendar is a rule-based calendar with comparatively simple rules (at least, compared to the astronomical calculation required for the Chinese Calendar). It is included in this software because it has an interesting connection to the Chinese Calendar.

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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