BS Date

A JavaScript library for converting between Anno Domini (AD/Gregorian) and Bikram Sambat (BS/Nepali) dates.

Installation

``bash
npm install bs-date
`

Features

- Convert Bikram Sambat dates to Anno Domini dates
- Convert Anno Domini dates to Bikram Sambat dates
- Supports BS years 2000-2090 (AD 1943-2034)
- Validates date ranges and throws appropriate errors
- Extends native Date prototype with toBS() method
- Format dates in Nepali script with toNepali()
- Get month names in Nepali or romanized format
- Get day names in Nepali, romanized, or localized English format
- Convert numbers to Nepali numerals

Usage

$3

`javascript
import BSDate from "bs-date";
import "bs-date/src/number-utils.js"; // For Nepali number conversion

// Create a BS date
const bsDate = new BSDate(2082, 5, 25);

// Convert to AD
const adDate = bsDate.toAD();
console.log(adDate); // 2025-09-10T00:00:00.000Z

// Convert AD date to BS
const adDate2 = new Date("2025-09-10");
const bsDate2 = BSDate.fromAD(adDate2);
console.log(bsDate2); // BSDate { year: 2082, month: 5, day: 25 }

// Format in Nepali
console.log(bsDate.toNepali()); // "भाद्र २५, २०८२"

// Get month and day names
console.log(bsDate.monthName()); // "भाद्र"
console.log(bsDate.monthName({ romanized: true })); // "Bhadra"
console.log(bsDate.dayName()); // "मंगलवार"
console.log(bsDate.dayName({ romanized: true })); // "Mangalbar"
console.log(bsDate.dayName({ localized: true })); // "Tuesday"
`

$3

`javascript
import "bs-date/src/date-utils.js";

const adDate = new Date("2025-09-10");
const bsDate = adDate.toBS();
console.log(bsDate); // BSDate { year: 2082, month: 5, day: 25 }
`

$3

For displaying dates in Nepali format using native JavaScript localization:

`javascript
const adDate = new Date("2025-09-10");

// Format AD date in Nepali locale (displays AD date in Nepali numerals)
console.log(adDate.toLocaleDateString("ne-NP")); // "२०२५/९/१०"

// For BS date formatting, combine both approaches
const bsDate = adDate.toBS();
console.log(BS Date: ${bsDate.toNepali()}); // "BS Date: भाद्र २५, २०८२"
console.log(AD Date (Nepali): ${adDate.toLocaleDateString("ne-NP")}); // "AD Date (Nepali): २०२५/९/१०"
`

Note: toLocaleDateString('ne-NP') formats the AD date in Nepali numerals and locale format, while toBS() and toNepali() provides the actual BS calendar date in Nepali script.

API Reference

$3

#### Constructor

`javascript
new BSDate(year, month, day);
`

- year (number): BS year (2000-2090)
- month (number): BS month (1-12)
- day (number): BS day (1-32, varies by month)

#### Methods

##### toAD()

Converts the BS date to an AD Date object.

Returns: Date - The equivalent AD date

Throws: BSDateOutOfRangeError - If the BS date is invalid or out of range

##### toNepali()

Formats the BS date in Nepali script.

Returns: string - The formatted date (e.g., "भाद्र २५, २०८२")

##### monthName(options)

Gets the month name in Nepali or romanized format.

Parameters:

- options (object, optional):
- romanized (boolean): If true, returns romanized month name

Returns: string - The month name

Examples:

`javascript
bsDate.monthName(); // "भाद्र"
bsDate.monthName({ romanized: true }); // "Bhadra"
`

##### dayName(options)

Gets the day name in various formats.

Parameters:

- options (object, optional):
- romanized (boolean): If true, returns romanized day name
- localized (boolean): If true, returns English day name

Returns: string - The day name

Throws: Error - If both romanized and localized are true

Examples:

`javascript
bsDate.dayName(); // "मंगलवार"
bsDate.dayName({ romanized: true }); // "Mangalbar"
bsDate.dayName({ localized: true }); // "Tuesday"
`

##### BSDate.fromAD(adDate)

Static method to create a BSDate from an AD Date.

Parameters:

- adDate (Date): The AD date to convert

Returns: BSDate - The equivalent BS date

$3

#### Date.prototype.toBS()

Converts an AD Date to BSDate.

Returns: BSDate - The equivalent BS date

Throws: DateOutOfRangeError - If the AD date is before April 14, 1943

$3

#### Number.prototype.toNepali()

Converts a number to Nepali numerals.

Returns: string - The number in Nepali numerals

Examples:

`javascript
import "bs-date/src/number-utils.js";

(123).toNepali(); // "१२३"
(2082).toNepali(); // "२०८२"
`

Supported Date Range

- BS Range: 2000/01/01 - 2090/12/30
- AD Range: April 14, 1943 - April 13, 2034

Error Handling

The library throws two types of errors:

$3

Thrown when:

- BS year is outside the supported range (2000-2090)
- BS month is invalid (not 1-12)
- BS day is invalid for the given month/year
- Required constructor parameters are missing

$3

Thrown when:

- AD date is before the supported epoch (April 14, 1943)

Examples

$3

`javascript
import BSDate, { BSDateOutOfRangeError } from "bs-date";

try {
const invalidDate = new BSDate(1999, 1, 1);
invalidDate.toAD();
} catch (error) {
if (error instanceof BSDateOutOfRangeError) {
console.log("BS date is out of range");
}
}
`

$3

`javascript
import BSDate from "bs-date";
import "bs-date/src/date-utils.js";
import "bs-date/src/number-utils.js";

const today = new Date();
const todayBS = today.toBS();
console.log(Today in BS: ${todayBS.year}/${todayBS.month}/${todayBS.day});
console.log(Today in Nepali: ${todayBS.toNepali()});
console.log(Today is ${todayBS.dayName({ localized: true })});
`

$3

`javascript
import BSDate from "bs-date";
import "bs-date/src/number-utils.js";

const bsDate = new BSDate(2082, 5, 18);

// Different formatting options
console.log("Default format:", bsDate.toNepali()); // "भाद्र १८, २०८२"
console.log("Month (Nepali):", bsDate.monthName()); // "भाद्र"
console.log("Month (English):", bsDate.monthName({ romanized: true })); // "Bhadra"
console.log("Day (Nepali):", bsDate.dayName()); // "बुधबार"
console.log("Day (English romanized):", bsDate.dayName({ romanized: true })); // "Budhbar"
console.log("Day (Localized):", bsDate.dayName({ localized: true })); // "Wednesday"

// Number conversion
console.log("Year in Nepali:", bsDate.year.toNepali()); // "२०८२"
console.log("Day in Nepali:", bsDate.day.toNepali()); // "१८"
`

BS Calendar Information

The library includes comprehensive data for Bikram Sambat calendar:

- Months: Baisakh, Jeth, Asar, Shrawan, Bhadra, Ashwin, Kartik, Mangsir, Poush, Magh, Falgun, Chaitra
- Variable month lengths depending on the year
- Accurate conversion based on established BS calendar data

Development

$3

`bash
npm test
`

$3

`bash
npm run lint
`

$3

`bash
npm run dev
``

License

This project is licensed under the MIT License - see the LICENSE file for details.

Author

Deepak Lamichhane