facebook.com | Activity Log Time Travel

// ==UserScript==
// @name        facebook.com | Activity Log Time Travel
// @match       https://www.facebook.com/*
// ==/UserScript==

function set(key, diff) {
  const url = new URL(window.location.href);
  const value = parseInt(url.searchParams.get(key));
  url.searchParams.set(key, value + diff);
  window.location.href = url.toString();
}

function inc_year(diff) {
  set('year', diff);
}

function inc_month(diff) {
  set('month', diff);
}

Object.assign(unsafeWindow, {inc_year, inc_month});

// bookmarklets
// y+ javascript:inc_year(1);void(0);
// y- javascript:inc_year(-1);void(0);
// m+ javascript:inc_month(1);void(0);
// m- javascript:inc_month(-1);void(0);