Run this on a course page to get the date the course was created and last updated.

udemy-get-createdDate.js

function getCourseId() {
    const courseEl = document.querySelector("body#udemy");

    if (!courseEl) throw new Error("Must be on a Udemy course page!");

    const id = courseEl.dataset.clpCourseId;

    if (!id) {
        // for active course
        const secondaryId = document.querySelector("#udemy > div.main-content-wrapper > div.main-content > div").dataset.moduleArgs;

        if (!secondaryId || !secondaryId.includes("courseId")) throw new Error("Couldn't get the course ID, make sure you're on the Udemy course page.");

        return JSON.parse(secondaryId).courseId;
    }

    return id;
}

fetch(`https://www.udemy.com/api-2.0/courses/${getCourseId()}/?fields[course]=created,last_update_date,published_time`)
    .then(res => res.json())
    .then(course => {
        console.log(course);
        console.info(`This course was created at ${(new Date(course.created)).toLocaleString()}, published at ${(new Date(course.published_time)).toLocaleString()}, and last updated on ${(new Date(course.last_update_date)).toLocaleString()}`);
    });

Basically, it just fetches the dates and prints the JSON and a pretty message in the console. I'll list the steps below to use it:

1. Go to a course page on Udemy (this can be the overview page or on a lecture)
2. Open the console for your web browser: Press F12 or CTRL + Shift + I or CMD + Shift + I or navigate the UI menus for the developer tools / console.
3. Paste the script in and run it.
4. Optionally, for Chrome browsers, save it to your snippets.