Advanced Usage

Switching calendars per call

Each method accepts an optional options argument. You can mix UAQ and FCNA in the same codebase:

import dayjs from 'dayjs';
import hijriPlugin from 'dayjs-hijri-plus';

dayjs.extend(hijriPlugin);

const d = dayjs('2023-03-23');

const uaqYear = d.hijriYear();                     // UAQ (default)
const fcnaYear = d.hijriYear({ calendar: 'fcna' }); // FCNA

Near month boundaries, UAQ and FCNA may differ by one day. The calendar argument is per-call, not session-wide.

Null safety

toHijri() returns null for dates outside the UAQ range (approximately 1900-2076 CE). Guard before using the result:

const h = d.toHijri();
if (h !== null) {
  console.log(h.hy, h.hm, h.hd);
}

Use isValidHijri() when you only need a boolean check.

Combining with Day.js plugins

dayjs-hijri-plus works alongside other Day.js plugins. The order of extend() calls matters when two plugins patch the same method. Register dayjs-hijri-plus after plugins that also modify .format():

import dayjs from 'dayjs';
import utc from 'dayjs/plugin/utc';
import timezone from 'dayjs/plugin/timezone';
import hijriPlugin from 'dayjs-hijri-plus';

dayjs.extend(utc);
dayjs.extend(timezone);
dayjs.extend(hijriPlugin);

const d = dayjs.utc('2023-03-23');
console.log(d.hijriYear()); // 1444

Mixing Gregorian and Hijri tokens

Hijri tokens (iYYYY, iMM, iDD, iMMMM, etc.) coexist with Day.js Gregorian tokens in formatHijri:

d.formatHijri('YYYY-MM-DD (iD iMMMM iYYYY)');
// '2023-03-23 (1 Ramadan 1444)'

Standard Day.js .format() still handles Gregorian-only strings normally. Use formatHijri only when you need Hijri tokens.

Tree-shaking

The package ships both ESM and CJS builds. ESM bundlers (Vite, esbuild, Rollup) eliminate unused code. The plugin is approximately 2 KB min+gz on top of Day.js.

TypeScript augmentation

The plugin augments the Day.js type definitions automatically. No separate type import is needed:

import dayjs from 'dayjs';
import hijriPlugin from 'dayjs-hijri-plus';

dayjs.extend(hijriPlugin);

const d = dayjs('2023-03-23');
const year: number = d.hijriYear()!; // fully typed; assert non-null if date is in range

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