API Reference

API Reference

Conversion functions

toHijri(date, options?)

Converts a Gregorian Date to a Hijri date object.

function toHijri(date: Date, options?: ConversionOptions): HijriDate | null;

Parameter	Type	Description
date	Date	Gregorian date to convert
options.calendar	string	Calendar name. Defaults to 'uaq'

Returns HijriDate or null if the date falls outside the calendar's supported range.

Throws Error('Invalid Gregorian date') if date is not a valid Date instance.

UAQ uses local date components (getFullYear, getMonth, getDate) for timezone-safe lookup. FCNA uses UTC components because its criterion is UTC-based.

toGregorian(hy, hm, hd, options?)

Converts a Hijri date to a Gregorian Date.

function toGregorian(hy: number, hm: number, hd: number, options?: ConversionOptions): Date | null;

Parameter	Type	Description
hy	number	Hijri year
hm	number	Hijri month (1-12)
hd	number	Hijri day (1-30)
options.calendar	string	Calendar name. Defaults to 'uaq'

Returns a UTC midnight Date or null if the input is out of range.

Throws Error('Invalid Hijri date') for UAQ when the date is not in the reference table.

isValidHijriDate(hy, hm, hd, options?)

Returns true if the given Hijri date exists in the selected calendar.

function isValidHijriDate(hy: number, hm: number, hd: number, options?: ConversionOptions): boolean;

daysInHijriMonth(hy, hm, options?)

Returns the number of days in a given Hijri month.

function daysInHijriMonth(hy: number, hm: number, options?: ConversionOptions): number;

Returns 29 or 30. Returns 0 for UAQ when the year is out of range.

Registry functions

registerCalendar(name, engine)

Registers a calendar engine. Overwrites any existing engine with the same name.

function registerCalendar(name: string, engine: CalendarEngine): void;

getCalendar(name)

Returns the registered engine for a given name. Throws if not found.

function getCalendar(name: string): CalendarEngine;

Throws Error('Unknown Hijri calendar: "name". Available: ...').

listCalendars()

Returns the names of all registered calendars.

function listCalendars(): string[];

Types

HijriDate

interface HijriDate {
  hy: number; // Hijri year
  hm: number; // Hijri month (1-12)
  hd: number; // Hijri day (1-30)
}

HijriYearRecord

One entry in the Umm al-Qura reference table.

interface HijriYearRecord {
  hy: number; // Hijri year
  dpm: number; // 12-bit days-per-month bitmask
  gy: number; // Gregorian year of 1 Muharram
  gm: number; // Gregorian month of 1 Muharram (1-based)
  gd: number; // Gregorian day of 1 Muharram
}

The dpm bitmask encodes month lengths. Bit i (0-indexed from bit 0) corresponds to month i+1: 1 = 30 days, 0 = 29 days.

CalendarEngine

interface CalendarEngine {
  readonly id: string;
  toHijri(date: Date): HijriDate | null;
  toGregorian(hy: number, hm: number, hd: number): Date | null;
  isValid(hy: number, hm: number, hd: number): boolean;
  daysInMonth(hy: number, hm: number): number;
}

ConversionOptions

interface ConversionOptions {
  calendar?: string; // defaults to 'uaq'
}

Data exports

Export	Type	Description
hDatesTable	HijriYearRecord[]	Full UAQ table, 184 entries (1318-1500 H) plus sentinel
hmLong	string[]	Long month names. Index 0 = Muharram
hmMedium	string[]	Medium month names
hmShort	string[]	Short month codes (3 chars)
hwLong	string[]	Long weekday names. Index 0 = Sunday
hwShort	string[]	Short weekday names
hwNumeric	number[]	Weekday numbers, 1 = Sunday, 7 = Saturday

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