Convert Gregorian Date to Islamic Date (Hijri)

islamic_date.js

/**
 * Uses JavaScripts Internationalization to convert a gregorian date into
 * an islamic hijri date. The W3C Spec included a format "ca-islamic" which
 * makes this all happen.
 */
export function getHijriDate(date = new Date()) {
  const locale = navigator.language
  return new Intl.DateTimeFormat(locale + '-u-ca-islamic', {
    day: 'numeric',
    month: 'long',
    year: 'numeric'
  }).format(date)
}