JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://momentjs.com/downloads/moment-with-locales.js"></script>

JavaScript

function getFirstDayOfFirstWeekByYear( year ) {
	let func = moment().year(year).startOf('year') // Edit here
	return func.format('D. MMMM YYYY (dddd)')
}





// Tester
[2017, 2016, 2015, 2014, 2013].forEach(function ( year ) {
	let s = '<li>' + getFirstDayOfFirstWeekByYear( year ) + '</li>'
 	document.getElementsByTagName('BODY')[0].innerHTML += s
})