JSFiddle - React, Tailwind, and code Playground

JavaScript

var now = new Date();
var start = new Date(now.getFullYear(), 0, 0);
var diff = now - start;
var oneDay = 1000 * 60 * 60 * 24;
var day = Math.floor(diff / oneDay);

var PROGRAMMERS_DAY = 256;
if(day === PROGRAMMERS_DAY) {
    alert('Happy programmer\'s day');
} else if (day > PROGRAMMERS_DAY) {
    alert('Just wait for next year.');
} else {
    alert('Just '+(PROGRAMMERS_DAY-day)+" more days");
}