converts between Hebrew and Gregorian dates using Rata Die (R.D.) algorithm by Dershowitz and Reingold
$ npm install @hebcal/hdateimport {greg, abs2hebrew} from '@hebcal/hdate';
const date = new Date(2008, 10, 13); // 13 November 2008
const abs = greg.greg2abs(date);
const hdate = abs2hebrew(abs); // {yy: 5769, mm: CHESHVAN, dd: 15}