thetkarit

Overview

This project focuses on Burmese calendar calculations and astronomy studies and is still under active development.

Most of the code in this repository is in the public domain or released under an open source license. However, some code and/or data may use different copyright terms (usually still an open source license). See Resources.

The package exports a default object with focused modules for calendar views, moon phases, sunrise and sunset calculations, time zone helpers, and small UI helpers.

Note: Variable-date holidays are handled in two ways: Thingyan and Myanmar New Year are calculated algorithmically, while holidays such as "Deepavali" and "Eid al-Adha" use maintained date tables.

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Node.js

Install

npm install thetkarit

ESM (JavaScript)

import thetkarit from "thetkarit";

const day = thetkarit.calendar.dayView({
  year: 2025,
  month: 2,
  day: 12,
  lang: "English",
});

console.log("Sasana Year:", day.burmese_cal.sasana_year.id);
console.log("Burmese Year:", day.burmese_cal.burmese_year.id);
console.log("Burmese Month:", day.burmese_cal.burmese_month.str);
console.log("Moon Phase:", day.burmese_cal.moon_phase.str);
console.log("Fortnight Day:", day.burmese_cal.fortnight_day.id);
console.log("Day in Burmese Month:", day.burmese_cal.burmese_day.id);
console.log("Public Holidays:", day.burmese_cal.public_holiday.join(", "));

TypeScript

import thetkarit from "thetkarit";

const day = thetkarit.calendar.dayView({
  year: 2025,
  month: 2,
  day: 12,
  lang: "English",
});

console.log("Sasana Year:", day.burmese_cal.sasana_year.id);
console.log("Burmese Year:", day.burmese_cal.burmese_year.id);
console.log("Burmese Month:", day.burmese_cal.burmese_month.str);
console.log("Moon Phase:", day.burmese_cal.moon_phase.str);
console.log("Fortnight Day:", day.burmese_cal.fortnight_day.id);
console.log("Day in Burmese Month:", day.burmese_cal.burmese_day.id);
console.log("Public Holidays:", day.burmese_cal.public_holiday.join(", "));

CommonJS

const thetkarit = require("thetkarit");

const day = thetkarit.calendar.dayView({
  year: 2025,
  month: 2,
  day: 12,
  lang: "English",
});

console.log("Sasana Year:", day.burmese_cal.sasana_year.id);
console.log("Burmese Year:", day.burmese_cal.burmese_year.id);
console.log("Burmese Month:", day.burmese_cal.burmese_month.str);
console.log("Moon Phase:", day.burmese_cal.moon_phase.str);
console.log("Fortnight Day:", day.burmese_cal.fortnight_day.id);
console.log("Day in Burmese Month:", day.burmese_cal.burmese_day.id);
console.log("Public Holidays:", day.burmese_cal.public_holiday.join(", "));

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TypeScript API

The default export exposes these runtime members:

• calendar
• moon
• sunTimes(options)
• zoneOffset(timeZone)
• zoneInfo(timeZone)
• timeZones
• timeZonesInfo
• ui.blankCells
• ui.numberRange

It also re-exports the main TypeScript types for calendar views, time zones, moon phases, and sun time calculations.

Calendar

import thetkarit from "thetkarit";

const month = thetkarit.calendar.monthView({
  year: 2025,
  month: 4,
  lang: "English",
});

const thingyan = thetkarit.calendar.thingyan(2025);
const julian = thetkarit.calendar.datetimeToJd({
  year: 2025,
  month: 4,
  day: 17,
  hour: 12,
  tz: "Asia/Yangon",
});

console.log(month.month.long);
console.log(thingyan.NewYearDay);
console.log(julian.jd, julian.jdn);

Available calendar methods:

• yearView({ year, lang })
• monthView({ year, month, lang })
• dayView({ year, month, day, lang })
• thingyan(year, yearType?)
• burmeseYearType(burmeseYear, lang?)
• datetimeToJd({ year, month, day, hour?, minutes?, seconds?, tz? })
• jdToDatetime(jd, tz?)
• calendarConverter({ ct, year, month, day })

Moon

import thetkarit from "thetkarit";

const phases = thetkarit.moon.moonPhaseStr(2025, 8);
const fullMoonDays = thetkarit.moon.fullmoonDay(2025, "Asia/Yangon");

console.log(phases.fullMoon);
console.log(fullMoonDays[0]);

Available moon methods:

• moonPhases(year, month)
• moonPhaseStr(year, month)
• fullmoonDay(year, tz?)
• moonAge(tz?)
• meenusLunationNumber(year, month)
• brownLunationNumber(year, month)
• thaiLunationNumber(year, month)

Note: the moon helpers use zero-based month values where 0 = January and 11 = December.

Sun And Time Zones

import thetkarit from "thetkarit";

const sun = thetkarit.sunTimes({
  latitude: 16.8661,
  longitude: 96.1951,
  date: new Date("2025-02-12T00:00:00Z"),
  timezone: "Asia/Yangon",
});

const offset = thetkarit.zoneOffset("Asia/Yangon");
const info = thetkarit.zoneInfo("Asia/Yangon");

console.log(sun.sunrise, sun.sunset, sun.daytime);
console.log(offset);
console.log(info?.countryName, info?.currentOffset);

Source Layout

The main modules under /src are organized as follows:

• src/index.ts: package entrypoint and public exports.
• src/calendar/: Burmese calendar, Gregorian conversions, translations, holidays, astrology days, and view builders.
• src/moon/: moon phase, full moon, lunation, and moon age calculations.
• src/suntime/: sunrise, sunset, and daytime duration calculations.
• src/timezones/: supported IANA time zones, offsets, and metadata.
• src/calendar/ui/: small helpers for calendar-oriented UI rendering.

Resources

Burmese Calendar

• The algorithm for calculating the Burmese Calendar (Myanmar Calendar) and astrological calendar days by Dr. Yan Naing Aye.

• References:

  https://cool-emerald.blogspot.com/2013/06/algorithm-program-and-calculation-of.html

  https://cool-emerald.blogspot.com/2013/12/myanmar-astrological-calendar-days.html

Julian Date and Moon Phases

• A collection of astronomy-related programs, algorithms, tutorials, and data, including an implementation of the algorithm from Meeus' Astronomical Algorithms for computing the dates of the Moon's phases, by Greg Miller ([email protected]).

• Reference: https://www.celestialprogramming.com/

Local sunrise and sunset times

• Based on the algorithm by Rui Okada: https://gist.github.com/ruiokada/b28076d4911820ddcbbc

• Computation references:

  • https://en.wikipedia.org/wiki/Julian_day#Converting_Julian_or_Gregorian_calendar_date_to_Julian_Day_Number
  • https://en.wikipedia.org/wiki/Sunrise_equation#Complete_calculation_on_Earth

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