The lunar calendar is not a vague folk tradition but a system governed by clear astronomical rules. Its central question is singular: how to simultaneously track the moon and the sun, ensuring that months follow lunar phases while years remain aligned with the four seasons.<\/p>\n\n\n\n
The historical evolution can be summarized. The ancient ‘Xia Calendar’ established the prototype of a system that began the year in the month of Yin. In 104 BC, the Western Han dynasty promulgated the ‘Taichu Calendar’, which first fully established a lunisolar calendar system that set the new moon as the start of the month and corrected the solar year with solar terms. In 1645, during the early Qing dynasty, the ‘Shixian Calendar’ was implemented, introducing Western astronomical calculation methods to derive new moons and solar terms based on actual celestial phenomena. Since then, the calendar has entered a phase based on precise astronomical calculations. The modern lunar calendar has developed along this technical trajectory.<\/p>\n\n\n\n
The specific calculation methods are regulated by the ‘Compilation and Issuance of the Lunar Calendar’ (GB\/T 33661-2017), implemented in mainland China in 2017. The principles are not mysterious and can be summarized in four steps.<\/p>\n\n\n\n
First, the month is determined by the astronomical new moon. When the moon and the sun have the same ecliptic longitude and the moon’s surface is not visible from Earth, this moment is called the new moon. According to Beijing time, the day of the new moon is designated as the first day of the month. A synodic month averages approximately 29.53 days, so lunar months alternate between 29 and 30 days without a fixed pattern.<\/p>\n\n\n\n
Second, the year is determined by solar terms. The Earth’s orbit around the sun creates 24 solar terms, with one term occurring every 15 degrees. Among these, 12 are ‘mid-terms’, such as the spring equinox, summer solstice, autumn equinox, and winter solstice. Mid-terms are crucial for correcting the calendar year.<\/p>\n\n\n\n
Third, a month without a mid-term is designated as a leap month. Twelve synodic months total about 354 days, which is roughly 11 days shorter than the tropical year of about 365.2422 days. To prevent solar terms from advancing each year, the rule states that if there is no mid-term between one new moon and the next, that month is designated as a leap month, retaining the name of the previous month. On average, there are about 19 leap months in 7 cycles, but the actual determination depends on the celestial phenomena of that year.<\/p>\n\n\n\n
Fourth, the eleventh month is determined by the winter solstice. The standard requires that the winter solstice must fall within the eleventh month of the lunar calendar. By calculating forwards and backwards from this point, it ensures that the first day of the lunar new year generally falls between late January and mid-February in the Gregorian calendar, maintaining the relative stability between the Spring Festival and the beginning of spring.<\/p>\n\n\n\n
The logic of this entire system is clear: the new moon addresses the ‘month’ issue, mid-terms address the ‘year’ issue, leap months resolve the discrepancies between the lunar and solar cycles, and the winter solstice establishes the sequence of the year. The tools for calculation may have evolved from counting rods to computers, but the principles remain unchanged.<\/p>\n\n\n\n
Thus, the lunar calendar is neither purely lunar nor purely solar; it is a lunisolar calendar based on astronomical observations. Its stability lies not in tradition but in rules.<\/p>\n\n\n\n
Time originates from celestial bodies, and calendars merely translate celestial phenomena into human order. What appears complex is, in fact, the repeated application of a few clear principles.<\/p>\n","protected":false},"excerpt":{"rendered":"
The lunar calendar is a yin-yang calendar based on astronomical observations, using clear calculation rules to track the movements of the moon and sun, ensuring the correspondence between seasons and months.<\/p>\n","protected":false},"author":2,"featured_media":2291,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"_wpas_customize_per_network":false},"categories":[85],"tags":[],"class_list":["post-2292","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-explainers"],"yoast_head":"\n