JSFiddle - React, Tailwind, and code Playground

by Arnaud

HTML

<div class="datepicker"></div>

CSS

.test{
  
  
  color:red !important;
  background:black;
}

JavaScript

var selectedDay = new Date().getTime();

$('.datepicker').datepicker({
    onSelect: function (date) {
        selectedDay = $(this).datepicker.getTime();
    },
    beforeShowDay: function (date) {
        var d = date.getTime();
        if (d < selectedDay && d < selectedDay + 1 + 86400000 * 29) {
            return [true, 'test', ''];
        } else {
            return [true, 'test2', ''];
        }
    }
});