This package provides functions to convert between the solar and lunar calendars, with a focus on the Vietnamese lunar calendar system. The lunar calendar depends on the time zone, longitude, and latitude, so it is recommended to use this package only for the Vietnamese lunar calendar.

All the functions are converted from Javascript to Dart. The original is from PhD. Ho Ngoc Duc. Thanks to him for inspiring me to create this package in Dart.

Features

• Convert Solar date to Lunar date and vice versa (supported from 1800 to 2199).
• Convert Solar date to Julian days.

Usage

• From version 1.1.0, the package supports Classes instead of Lists for easier access. Lunar and Solar provide methods to interact with each other, or converted to DateTime object.

  final lunar = Lunar(createdFromSolar: true, date: DateTime(1998, 6, 18));
  final solar = Solar(DateTime(1998, 6, 18));
  final convertedSolarFromLunar = lunar.getSolar();
  
  // solar == convertedSolarFromLunar -> true

• The convertSolar2Lunar function returns a List by order: [lunarDay, lunarMonth, lunarYear, leap], where leap indicates whether the lunarMonth is a leap or not.

int dd = 23;
int mm = 3;
int yy = 2023;
int timeZone = 7; 

List<int> lunar = convertSolar2Lunar(dd, mm, yy, timeZone); // lunar = [2, 2, 2023, 1] - leap

• The convertLunar2Solarfunction returns a List by order [solarDay, solarMonth, solarYear]. Note that it takes the leap parameter, where leap = 1 if the lunarMonth is leap, 0 if it is not leap.

int dd = 2;
int mm = 2;
int yy = 2023;
int leap = 1;
int timeZone = 7;

List<int> solar = convertLunar2Solar(dd, mm, yy, leap, timeZone); // solar = [23, 3, 2023]

Additional information

I recommend reading the original research from PhD. Ho Ngoc Duc to know more about the calculation.