Solarlunar

Solarlunar is a lightweight open-source JavaScript library that provides conversion between the solar (Gregorian) calendar and the traditional Chinese lunar calendar. It is designed to help software applications display or work with dates in either system, and to support commonly used operations such as determining the corresponding lunar date for a given Gregorian date, and converting a lunar date back to a Gregorian date.

The core functionality centers on two primary operations: solarToLunar and lunarToSolar. SolarToLunar accepts a year, month, and day in the Gregorian calendar and returns the corresponding lunar year, lunar month, day, and an indicator for leap months when applicable. LunarToSolar performs the reverse conversion, taking a lunar year, month, day, and leap-month flag, and returning the corresponding Gregorian date. The library relies on predefined data tables that encode leap months, month lengths, and other calendar rules for a range of years.

Solarlunar is commonly used in web applications and Node.js environments that need to display lunar dates for festivals, horoscopes, or cultural features. As an open-source tool, it is typically bundled with other date utilities and integrated into user interfaces, calendars, or tools that require bilingual or cross-calendar support.

Limitations can include reliance on a fixed data set for lunar rules, which may vary by region or calendar convention, and potential edge cases around leap months or historical calendar changes. Users should verify results for their specific cultural or regional requirements. See also: Chinese calendar, lunar calendar, solar terms.