A Javascript library to calculate Tibetan calendrical dates according
to the Phugpa tradition.

The calculations are basically implementation the formulas in Svante Janson,
"Tibetan Calendar Mathematics". We are using year 806 as the epoch for all calculations. See the paper for details.

Installation

npm install tibetan-date-calculator

Usage

``javascript
import { TibetanDate, TibetanMonth, TibetanYear } from 'tibetan-date-calculator';
`

API

The API exposes 3 classes: TibetanDate, TibetanMonth, TibetanMonth

TibetanDate

`javascript
tibDate = new TibetanDate(arg)
`

__arg__: __undefined__

This will return tibeatan date object for today.

__arg__: __String__

This will return tibetan date object for the _wester date_ new Date(arg).

__Note__: using date string without time stamp (e.g. '2019-06-21') can create bugs when run in different timezones due to the way native Date object handles it. See Date documentation

__arg__: __Object__

This will return tibetan day according to object definition:

| keys | type | default | description |
| -------------- | --------- | ------- | ---------------------------------------------------- |
| year | number | | Tibetan year number (ex. 2135) |
| month | number | | Tibetan month number (1 to 12) |
| isLeapMonth | boolean | false | is this month a leap month (first of repeated months)|
| day | number | | Tibetan day number (1 to 30) |
| isLeapDay | boolean | false | is this day a leap day (first of repeated day) |

#### Properties

These can be accessed directly tibDate.property

| property | type | description |
| ------------------- | -------------- | ---------------------------------------------------- |
| westernDate | Date | a JS Date object corresponding to this date |
| year | number | Tibetan year number (ex. 2135) |
| month | number | Tibetan month number (1 to 12) |
| date | number | Tibetan date number (1 to 30) |
| day | number | day of the week, same as calling westernDate.getDay() |
| yearObj | TibetanYear | |
| monthObj | TibetanMonth | |
| isDoubledDay | boolean | |
| isLeapDay | boolean | |
| isSkippedDay | boolean | is this date skipped in the Tibetan calendar |
| isPreviousSkipped | boolean | is the previous date skipped (e.g. date=3 is 2 skipped) |
| westernDateStr | string | YYYY-MM-DD |

#### Methods

TibetanDate exposes a set of methods to mimic the native Date behaviour.

| method | returns | description |
| ------------------- | -------------- | ----------------------------------- |
| getWesternDate() | Date | same as the property westernDate |
| getYear() | number | same as the property year |
| getMonth() | number | same as the property month |
| getDate() | number | same as the property date |
| getDay() | number | same as the property day |
| getMonthObj() | TibetanMonth | same as the property monthObj |
| getYearObj() | TibeatnYear | same as the property yearObj |
| toString() | string | returns 'year-month(-leap/-main)-date(-leap/-main)' |

TibetanMonth

`javascript
tibMonth = new TibetanMonth(arg)
`

__arg__: __undefined__

This will return tibeatan month object that includes today.

__arg__: __String__

This will return tibetan month object that includes the _wester date_ new Date(arg).

__arg__: __Object__

This will return tibetan month according to object definition:

| keys | type | default | description |
| -------------- | --------- | ------- | ---------------------------------------------------- |
| year | number | | Tibetan year number (ex. 2135) |
| month | number | | Tibetan month number (1 to 12) |
| isLeapMonth | boolean | false | is this month a leap month (first of repeated months)|

#### Properties

These can be accessed directly tibDate.property

| property | type | description |
| ------------------- | -------------- | ---------------------------------------------------- |
| year | number | Tibetan year number (ex. 2135) |
| month | number | Tibetan month number (1 to 12) |
| isLeapMonth | boolean | is this month a leap month (first of repeated months)|
| isDoubledMonth | boolean | is this month doubled (either leap or main) |
| startDateStr | string | western date string for the first date of the month |
| endDateStr | string | western date string for the last date of the month |
| yearObj | TibetanYear | TibetanYear object |
| days | TibetanDate[]| list of days in the month, skipped days are not included. Need to call getDays() on the instance at least once to calculate it |
| toString() | string | returns 'year-month(-leap/-main)' |

#### Methods

| method | returns | description |
| ------------------- | -------------- | ---------------------------------------------------- |
| getDays() | TibetanDate[]| generates an array of TibetanDays within this month, excluding skipped days. Once called, the days property will be populated too. |

TibetanYear

`javascript
tibYear = new TibetanYear(arg, isWestern = false)
`

__arg__: __undefined__

This will return tibeatan year object that includes today.

__arg__: __Number__

This will return tibetan year passed, unless isWestern is set to true. In that case the arg will be interpreted as a western year number.

__arg__: __Object__

This will return tibetan year according to rabjung year definition:

| keys | type | description |
| -------------- | --------- | ------------------------------------------ |
| rabjungCycle | number | The rabjung cycle number |
| rabjungYear | number | The year within the cycle (1 - 60) |

#### Properties

These can be accessed directly tibDate.property

| property | type | description |
| --------------- | --------- | ---------------------------------------------------- |
| rabjungCycle | number | |
| rabjungYear | number | |
| tibYearNum | number | |
| westernYear | number | |
| animal | string | |
| element | string | |
| gender | string | |
| months | TibetanMonth[]| need to call getMonth() on the instance at least once to calculate it |

#### Methods

| method | returns | description |
| ------------------- | --------------- | ---------------------------------------------------- |
| getMonths() | TibetanMonth[]| generates an array of TibetanMonth within this year. Once called, the months property will be populated too. |
| toRabjungString() | string | returns 'The X. year of the Y. rabjung cycle' |
| toString() | string` | returns the Tibetan year number as string |

Examples ##