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Comprehensive BS/AD calendar and Nepali localization toolkit for Dart and Flutter.

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nepali_kit #

A production-quality, all-in-one Nepali calendar, localization, and UI toolkit for Dart and Flutter.

pub package license tests

Package Introduction #

nepali_kit provides an enterprise-ready suite of utilities for building Nepali applications in Dart and Flutter. It provides high-speed Bikram Sambat (BS) calendar calculations, verified bidirectional BS ↔ AD date conversions, pattern-based date formatting, South Asian number & currency systems, number-to-words conversions, official fiscal year calculations, public holidays datasets, and Flutter Material 3 calendar and date picker widgets.

Screenshots & Visual Showcase #

Bikram Sambat Calendar Dual BS + AD Calendar Material 3 Date Picker
Bikram Sambat Calendar Dual BS + AD Calendar Material 3 Date Picker
Date Range Picker Bidirectional Conversion Custom Day Rendering
Date Range Picker BS AD Date Conversion Custom Day Rendering
Events & Holidays Fiscal Year & Quarters Numbers & Unicode Utilities
Events and Holidays Fiscal Year and Quarters Numbers and Unicode Utilities

Why this package? #

In the Dart & Flutter ecosystem, building a Nepali app typically requires stitching together 4 to 6 disparate packages:

  • One package for basic BS date calculations,
  • Another for number/Devanagari formatting,
  • Another for fiscal year math,
  • Another for holiday listings,
  • And yet another for Flutter calendar UI or date pickers.

This fragmentation leads to:

  1. Conflicting types (e.g. incompatible NepaliDateTime models across libraries),
  2. Inconsistent calendar tables (subtle discrepancies between day counts across years),
  3. Timezone bugs (hidden UTC/local conversion side-effects altering days),
  4. Maintenance debt and dependency hell.

nepali_kit solves this once and for all. It offers a single, cohesive, thoroughly tested foundation with zero external dependencies in its pure Dart core.

Features #

  • Calendar Engine: Immutable NepaliDate (date-only) and NepaliDateTime (date + time) with equality, comparisons, date ranges, and arithmetic.
  • Date Conversion: Verified bidirectional conversion ($\text{BS} \leftrightarrow \text{AD}$) with round-trip invariance across 1975 BS to 2099 BS.
  • Formatting & Parsing: ICU-style format tokens (yyyy, MMMM, dd, EEEE, hh:mm a) supporting English and Nepali Devanagari locales, plus dual date formatting.
  • Numbers: South Asian comma grouping (12,34,567.89) and conversion between ASCII digits (0-9) and Devanagari numerals (०-९).
  • Currency: Currency formatting with custom or localized currency symbols (रु 12,34,567.89 / Rs. 12,34,567.89).
  • Unicode/Text (Number to Words): Conversion of numeric amounts into spoken words in both Nepali (एक लाख तेइस हजार) and English up to Kharba and Arab.
  • Relative Time (Nepali Moments): Human-friendly relative time strings ("भर्खरै", "५ मिनेट अगाडि", "हिजो", "भोलि") in Nepali and English.
  • Fiscal Year: Accurate Nepali government fiscal year (NepaliFiscalYear) starting Shrawan 1 and ending Ashadh end, with automatic Q1–Q4 breakdowns.
  • Holidays: Built-in national gazetted holidays database for standard years with full support for custom corporate/organization holiday providers.
  • Flutter Calendar: Customizable Material 3 NepaliCalendarView and ADCalendarView with multi-event dots, custom builders, and theme support.
  • Date Pickers: showNepaliDatePicker, showNepaliDateRangePicker, NepaliMonthPicker, and NepaliYearPicker.
  • Calendar Events: Decoupled CalendarEvent model with category support, custom metadata, and multi-event day indicators.

Installation #

Add nepali_kit to your pubspec.yaml:

dependencies:
  nepali_kit: "<latest_release>"

Pure Dart (Backend / CLI / Scripts) #

For servers (Dart Frog, Serverpod), scripts, or CLI apps with zero Flutter dependencies:

import 'package:nepali_kit/nepali_kit_core.dart';

Flutter Applications #

For Flutter apps requiring UI widgets, calendar pickers, and themes:

import 'package:nepali_kit/nepali_kit.dart';

Quick Start #

import 'package:nepali_kit/nepali_kit.dart';

void main() {
  // Current Bikram Sambat date
  final today = NepaliDate.now();
  print('Today in BS: $today'); // e.g. 2081-06-13

  // Format with Nepali locale
  final formatted = NepaliDateFormat('EEEE, MMMM d, yyyy', Language.nepali).format(today);
  print('Formatted: $formatted'); // e.g. आइतबार, आश्विन १३, २०८१

  // Numbers to words
  final words = NepaliNumberToWords.convert(125000, language: Language.nepali);
  print('In words: $words'); // एक लाख पच्चीस हजार
}

BS ↔ AD Examples #

Convert seamlessly between Bikram Sambat and Gregorian calendars:

import 'package:nepali_kit/nepali_kit_core.dart';

// BS to AD
final bsDate = NepaliDate(2081, 6, 13);
final adDateTime = bsDate.toDateTime(); // 2024-09-29 00:00:00.000

// AD to BS
final gregorian = DateTime(2024, 9, 29);
final convertedBs = NepaliDate.fromDateTime(gregorian); // 2081-06-13

// Direct low-level converter
final (year, month, day) = BsAdConverter.bsToAd(2081, 6, 13);
final (bsY, bsM, bsD) = BsAdConverter.adToBs(year, month, day);

// Fluent DateTime extension
final bsFromExt = DateTime(2024, 9, 29).toNepaliDate();

NepaliDate Examples #

Construction & Validation #

// Valid date
final date = NepaliDate(2081, 6, 13);

// Today
final now = NepaliDate.now();

// Properties
print(date.year); // 2081
print(date.month); // 6
print(date.day); // 13
print(date.weekday); // 1 (Sunday / आइतबार)
print(date.monthNameNepali); // आश्विन
print(date.daysInMonth); // 30
print(date.isLeapYear); // false
print(date.startOfMonth); // 2081-06-01
print(date.endOfMonth); // 2081-06-30

Date Arithmetic #

final start = NepaliDate(2081, 3, 32); // Ashadh 32

// Adding days
final after10Days = start.addDays(10); // 2081-04-10 (handles month rollover)

// Month rollover with day-clamping
final nextMonth = start.addMonths(1); // Clamps to max days of Shrawan

// Year rollover
final nextYear = start.addYears(1); // 2082-03-31 (or 32 depending on year data)

// Difference between dates
final daysBetween = after10Days.differenceInDays(start); // 10

Comparisons & Ranges #

final d1 = NepaliDate(2081, 1, 1);
final d2 = NepaliDate(2081, 1, 15);

print(d1 < d2); // true
print(d1.isBefore(d2)); // true

// Date ranges
final range = NepaliDateRange(start: d1, end: d2);
print(range.durationInDays); // 14
print(range.days.length); // 15 dates

Formatting Examples #

Use NepaliDateFormat with standard pattern tokens across English and Nepali locales:

final dt = NepaliDateTime(2081, 6, 13, 15, 30, 45);

// English locale
final enFormat = NepaliDateFormat('yyyy-MM-dd HH:mm', Language.english);
print(enFormat.format(dt)); // 2081-06-13 15:30

// Nepali Devanagari locale
final npFormat = NepaliDateFormat('EEEE, MMMM dd, yyyy', Language.nepali);
print(npFormat.format(dt)); // आइतबार, आश्विन १३, २०८१

// Dual date formatting (BS + AD together)
final dual = NepaliDateFormat.formatDual(dt, language: Language.nepali);
print(dual); // "२०८१ आश्विन १३ (2024-09-29)"

Supported Pattern Tokens #

Token Description Output (English) Output (Nepali)
yyyy 4-digit Year 2081 २०८१
yy 2-digit Year 81 ८१
MMMM Full Month Name Ashwin आश्विन
MMM Short Month Name Ashw आ
MM 2-digit Month 06 ०६
M 1-digit Month 6 ६
dd 2-digit Day 13 १३
d 1-digit Day 13 १३
EEEE Full Weekday Sunday आइतबार
EEE Short Weekday Sun आइत
HH 24-Hour (00–23) 15 १५
hh 12-Hour (01–12) 03 ०३
mm Minute (00–59) 30 ३०
ss Second (00–59) 45 ४५
a AM / PM marker PM अपराह्न

Number Examples #

Grouping and Digits #

Format numbers with South Asian grouping (last 3 digits, then groups of 2 digits):

import 'package:nepali_kit/nepali_kit_core.dart';

// South Asian comma grouping (English numerals)
NepaliNumberFormat.format(1234567.89); // "12,34,567.89"

// South Asian comma grouping (Devanagari numerals)
NepaliNumberFormat.format(1234567.89, language: Language.nepali); // "१२,३४,५६७.८९"

// Digit conversion
NepaliDigits.toNepali(2081); // "२०८१"
NepaliDigits.toEnglish('२०८१'); // "2081"

Numbers to Words #

Convert numbers to spoken words up to Kharba and Arab:

// Nepali words
NepaliNumberToWords.convert(123456, language: Language.nepali);
// "एक लाख तेइस हजार चार सय छपन्न"

// English words
NepaliNumberToWords.convert(123456, language: Language.english);
// "One Lakh Twenty Three Thousand Four Hundred Fifty Six"

// Decimals and negatives
NepaliNumberToWords.convert(-50.75, language: Language.nepali);
// "ऋण पचास दशमलव सात पाँच"

Currency Examples #

Format monetary amounts with standard symbols:

// Nepali currency format
NepaliNumberFormat.currency(52450.50, language: Language.nepali);
// "रु ५२,४५०.५०"

// English currency format
NepaliNumberFormat.currency(52450.50, language: Language.english);
// "Rs. 52,450.50"

// Custom currency symbol
NepaliNumberFormat.currency(52450, customSymbol: 'NPR');
// "NPR ५२,४५०"

Fiscal Year Examples #

Nepal's fiscal year runs from Shrawan 1 to Ashadh end (mid-July to mid-July):

import 'package:nepali_kit/nepali_kit_core.dart';

// Fiscal year from date
final date = NepaliDate(2081, 6, 13);
final fy = NepaliFiscalYear.fromDate(date);

print(fy.label); // "2081/82"
print(fy.shortLabel); // "81/82"
print(fy.startDate); // 2081-04-01 (Shrawan 1)
print(fy.endDate); // 2082-03-31 (Ashadh end)

// Fiscal Quarters
final quarter = fy.quarterForDate(date);
print(quarter.quarter); // FiscalQuarter.first (Q1: Shrawan - Ashwin)
print(quarter.startDate); // 2081-04-01
print(quarter.endDate); // 2081-06-30

Holiday Examples #

Query national gazetted holidays or inject custom organization holidays:

import 'package:nepali_kit/nepali_kit_core.dart';

// Check if a date is a public holiday
final date = NepaliDate(2081, 1, 1);
if (HolidayService.isHoliday(date)) {
  final holidays = HolidayService.holidaysOn(date);
  for (final h in holidays) {
    print('${h.nameNepali} (${h.nameEnglish}) - Public: ${h.isPublic}');
  }
}

// Custom holiday provider for companies or schools
HolidayService.registerProvider(CustomHolidayProvider([
  NepaliHoliday(
    date: NepaliDate(2081, 5, 20),
    nameNepali: 'कम्पनी स्थापना दिवस',
    nameEnglish: 'Company Foundation Day',
    isPublic: true,
  ),
]));

// Reset back to official national holidays
HolidayService.reset();

Calendar Examples #

Embed interactive BS or AD calendars into your Flutter widgets:

import 'package:flutter/material.dart';
import 'package:nepali_kit/nepali_kit.dart';

class CalendarDemo extends StatefulWidget {
  @override
  State<CalendarDemo> createState() => _CalendarDemoState();
}

class _CalendarDemoState extends State<CalendarDemo> {
  NepaliDate _selectedDate = NepaliDate.now();

  @override
  Widget build(BuildContext context) {
    return NepaliCalendarView(
      initialDate: _selectedDate,
      selectedDate: _selectedDate,
      language: Language.nepali,
      onDateSelected: (date) {
        setState(() => _selectedDate = date);
      },
      events: [
        CalendarEvent(
          date: NepaliDate(2081, 6, 15),
          title: 'Project Deadline',
          category: 'work',
        ),
      ],
    );
  }
}

Date Picker Examples #

Open a familiar Material 3 modal date picker adapted for Bikram Sambat:

final picked = await showNepaliDatePicker(
  context: context,
  initialDate: NepaliDate.now(),
  firstDate: NepaliDate(2070, 1, 1),
  lastDate: NepaliDate(2090, 12, 30),
  language: Language.nepali,
  confirmText: 'छान्नुहोस्',
  cancelText: 'रद्द गर्नुहोस्',
);

if (picked != null) {
  print('Selected BS date: $picked');
}

Range Picker Examples #

Allow users to select an inclusive date span:

final pickedRange = await showNepaliDateRangePicker(
  context: context,
  firstDate: NepaliDate(2075, 1, 1),
  lastDate: NepaliDate(2085, 12, 30),
  language: Language.nepali,
);

if (pickedRange != null) {
  print('Range start: ${pickedRange.start}');
  print('Range end: ${pickedRange.end}');
  print('Total days: ${pickedRange.durationInDays}');
}

Events #

Manage calendar events and render multi-indicator badges:

final eventList = [
  CalendarEvent(
    date: NepaliDate(2081, 7, 15),
    title: 'Laxmi Puja',
    color: Colors.amber,
  ),
  CalendarEvent(
    date: NepaliDate(2081, 7, 15),
    title: 'Family Gathering',
    color: Colors.purple,
  ),
];

final collection = CalendarEventCollection(eventList);
print(collection.hasEvents(NepaliDate(2081, 7, 15))); // true
print(collection.eventsForDate(NepaliDate(2081, 7, 15)).length); // 2

Romanized Nepali → Unicode Transliteration #

Convert English literal phonetic Romanized Nepali into clean Devanagari Unicode using NepaliUnicode:

Basic Conversion #

import 'package:nepali_kit/nepali_kit.dart';

// Greetings & conversation
final greeting = NepaliUnicode.convert(
  "namaste, tpaaii'laaii kasto chha?",
);
print(greeting);
// नमस्ते, तपाईंलाई कस्तो छ?

// Everyday sentences
final sentence = NepaliUnicode.convert(
  "mero naam Bikash ho, ma nepaalmaa baschhu.",
);
print(sentence);
// मेरो नाम् बिकश् हो, म नेपाल्मा बस्छु.

Live (Type-as-you-write) Conversion #

For interactive input fields, set live: true to prevent premature character locking while the user continues typing:

TextField(
  onChanged: (text) {
    final liveNepali = NepaliUnicode.convert(
      text,
      live: true,
    );
    print(liveNepali);
  },
);

As the user types incrementally:

  • m → म्
  • ma → म
  • maa → मा
  • maala → माल
  • maalaa → माला

Notation Reference #

  • Vowels: a (अ), A / aa (आ), i (इ), I / ii (ई), u (उ), U / uu (ऊ), e (ए), E / ai (ऐ), o (ओ), au (औ)
  • Special Marks: ' (Anusvara ं), '' (Chandrabindu ँ), : (Visarga ः), | (Danda ।), || (Double Danda ॥), om / Om (ॐ)
  • Consonant aspirated forms: kh (ख्), gh (घ्), ch (छ्), jh (झ्), th (थ्), dh (ध्), ph/f (फ्), bh (भ्), sh (श्)
  • Retroflex consonants: T (ट्), Th (ठ्), D (ड्), Dh (ढ्), N (ण्), S (ष्)
  • Digits: 0-9 automatically map to ०-९
  • Non-Nepali Content Preservation: URLs (https://...), email addresses (user@domain.com), and already-Devanagari Unicode characters are detected and preserved without corruption.

Localization #

nepali_kit provides first-class support for both English (Language.english) and Nepali (Language.nepali). All UI components, date pickers, month names, weekday labels, and number formatters accept a Language parameter.

// Relative time in Nepali
final past = NepaliDate.now().subtractDays(2);
print(NepaliMoment.fromNepaliDate(past, language: Language.nepali)); // "२ दिन अगाडि"

// Relative time in English
print(NepaliMoment.fromNepaliDate(past, language: Language.english)); // "2 days ago"

Architecture #

nepali_kit enforces a strict architectural boundary between pure Dart logic and Flutter UI widgets:

nepali_kit/
├── lib/
│   ├── nepali_kit_core.dart       <-- Pure Dart entry point (zero Flutter dependencies)
│   │   ├── src/calendar/          (NepaliDate, NepaliDateTime, ranges, months)
│   │   ├── src/conversion/        (BS <-> AD conversion lookup table engine)
│   │   ├── src/formatting/        (NepaliDateFormat, token parser)
│   │   ├── src/numbers/           (NepaliDigits, NepaliNumberFormat, NumberToWords)
│   │   ├── src/fiscal/            (NepaliFiscalYear, quarters)
│   │   ├── src/holidays/          (Holiday models, datasets, service)
│   │   ├── src/relative_time/     (NepaliMoment)
│   │   ├── src/events/            (CalendarEvent model)
│   │   ├── src/text/              (NepaliUnicode transliteration engine)
│   │   └── src/core/              (Exceptions, constants, Language enum)
│   │
│   └── nepali_kit.dart            <-- Unified entry point for Flutter apps
│       └── src/flutter/           (NepaliCalendarView, pickers, dialogs, themes)
  • Backend / CLI safe: nepali_kit_core.dart has zero Flutter imports and compiles seamlessly on Serverpod, Dart Frog, or command-line scripts.
  • Pure-Dart testability: Core calendar algorithms are verified through pure-Dart unit tests independently of the Flutter engine.

Supported Date Range #

Calendar Minimum Date Maximum Date
Bikram Sambat (BS) 2000-01-01 BS (or 1975-01-01 BS in verified table) 2099-12-30 BS
Gregorian (AD) 1918-04-13 AD 2043-04-13 AD
  • Verified calendar tables guarantee exact month lengths matching official Nepalese Patro records across all 125 supported years.
  • Attempting to construct a NepaliDate outside this range throws a descriptive NepaliDateException.

Limitations #

  • Astronomical Predictions beyond 2099 BS: Because the Bikram Sambat calendar is governed by solar-lunar astronomical positions published annually by Nepal's Panchanga Nirnayak Samiti, years beyond 2099 BS are not pre-calculated to prevent historical drift.
  • Tithi Calculations: Lunar Tithis (such as Ekadashi, Purnima, Amavasya) depend on precise planetary coordinates at specific longitudes and are not included in this calendar engine.

Examples #

A comprehensive Flutter example application is included in the example/ directory demonstrating:

  1. Pure BS calendar with day selection,
  2. Dual BS + AD calendar,
  3. Multi-event indicators,
  4. Material 3 modal date picker and range picker,
  5. Dark theme and localization switching.

To run the example app:

cd example
flutter run

Testing #

The package includes an extensive test suite verifying mathematical invariants, boundary conditions, and UI interactions:

# Run pure Dart and widget tests
flutter test

# Run static analysis
flutter analyze

License #

This package is released under the MIT License.

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Comprehensive BS/AD calendar and Nepali localization toolkit for Dart and Flutter.

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Topics

#calendar #nepali #bikram-sambat #date-picker #localization

License

MIT (license)

Dependencies

flutter, meta

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