JSFiddle - React, Tailwind, and code Playground

HTML

<div class="col-sm-10">
  <input type="datetime-local" class="StartTime" data-department="12" name="bdaytime">
</div>

<div class="col-sm-10">
  <input type="datetime-local" class="StartTime" data-department="13" name="bdaytime">
</div>

<button>
  Clear
</button>

JavaScript

$('button').click(function(){
	$('input[data-department*="1"]').val('');
});