Convert MAM time to local time

convert.user.js

// ==UserScript==
// @name MAM Convert to Local Time
// @namespace hjdarnel
// @version 0.0.1
// @description Change displayed time and date to your timezone without seconds
// @author hjdarnel
// @match *://*.myanonamouse.net/*
// @grant none
// @icon https://www.myanonamouse.net/favicon.ico
// @downloadURL https://gist.githubusercontent.com/hjdarnel/4cf96197a53f18d64a69c7db058d6a72/raw/convert.user.js
// @updateURL https://gist.githubusercontent.com/hjdarnel/4cf96197a53f18d64a69c7db058d6a72/raw/convert.user.js
// ==/UserScript==

"use strict";

// Format date without seconds
function formatDateWithoutSeconds(date) {
  return date.toLocaleString([], {
    year: "numeric",
    month: "short",
    day: "numeric",
    hour: "numeric",
    minute: "2-digit",
  });
}

function updateTime(element) {
  let originalDateStr = element.getAttribute("data-original-date");

  if (!originalDateStr) {
    originalDateStr = element.innerText;
    element.setAttribute("data-original-date", originalDateStr);
  }

  // Parse date and adjust to show current time
  const date = new Date(originalDateStr + " UTC");
  const currentTime = new Date();
  const secondsDiff = Math.floor(
    (currentTime - new Date(originalDateStr + " UTC")) / 1000
  );

  date.setSeconds(date.getSeconds() + secondsDiff);
  const formattedDate = formatDateWithoutSeconds(date);

  // Only update DOM if the text has changed
  if (element.innerText !== formattedDate) {
    element.innerText = formattedDate;
  }
}

// Set up observers and periodic updates
function initialize() {
  const dateElements = document.querySelectorAll("#preNav > div");

  dateElements.forEach((element) => {
    updateTime(element);

    // Observe for changes
    const observer = new MutationObserver(() => updateTime(element));
    observer.observe(element, { childList: true });

    // Periodically update to keep time current
    setInterval(() => updateTime(element), 10000);
  });
}

// Run when DOM is ready
if (document.readyState === "loading") {
  document.addEventListener("DOMContentLoaded", initialize);
} else {
  initialize();
}