public-html/res/js/dynamic-content.js

const christmas = isItChristmas();

if (christmas) {
    var head = document.getElementsByTagName('head')[0];
    var snowJS = document.createElement("script");
    snowJS.type = "text/javascript";
    snowJS.src = "./res/js/snowstorm.js";
    head.appendChild(snowJS);

    const profileImage = document.querySelector("img.profile-image");
    profileImage.src = "./res/images/profile-christmas.jpg";
}

function isItChristmas() {
    const currentDate = new Date();
    const currentYear = currentDate.getFullYear();
    const startDate = new Date(`${currentYear}-11-10`);
    const endDate = new Date(`${currentYear + 1}-03-01`);
    return currentDate > startDate && currentDate < endDate;
}