JSFiddle - React, Tailwind, and code Playground

HTML

GENNAIO 2018
<table>
	<thead>
		<tr>
			<td class="inteBloc">LUNEDI</td>
			<td class="inteBloc">MARTEDI</td>
			<td class="inteBloc">MERCOLEDI</td>
			<td class="inteBloc">GIOVEDI</td>
			<td class="inteBloc">VENERDI</td>
			<td class="inteBloc">SABATO</td>
			<td class="inteBloc">DOMENICA</td>
			<td class="inteBloc">Ore</td>
			<td class="inteBloc">FestivitĂ </td>
		</tr>
	</thead>
	<tbody>
		<tr>
			<td>01</td>
			<td>02</td>
			<td>03</td>
			<td>04</td>
			<td>05</td>
			<td>06</td>
			<td>07</td>
			<td class="no"></td>
			<td class="no"></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
			<td class="no"></td>
			<td class="no"></td>
		</tr>
	</tbody>
</table>

JavaScript

var day;var CLASS;
var TD = document.getElementsByTagName('td');
var data = new Date(2018, 0, 1);
var millisec =  data.getTime();
for(let i = 0 ; i < TD.length ; i++){
		if(TD[i].className=='inteBloc' || TD[i].className=='no') continue
   
    
    data.setTime(millisec);
    
    
    TD[i].textContent=data.getDate();
    
    millisec += 86400000;
}