Countdown till Crimmus or any other date you want to use.

days-till-christmas.js

// Credit: https://www.w3resource.com/javascript-exercises/javascript-basic-exercise-9.php

today = new Date();
let cmas = new Date(today.getFullYear(), 11, 25);
if (today.getMonth() == 11 && today.getDate() > 25) {
  cmas.setFullYear(cmas.getFullYear() + 1); 
}  
let one_day = 1000 * 60 * 60 * 24;
console.log(Math.ceil((cmas.getTime() - today.getTime()) / (one_day)) + " days left until Christmas!");