diff --git a/browser/components/urlbar/tests/ext/api.js b/browser/components/urlbar/tests/ext/api.js
index 259925fbdda9..892e7a416cd7 100644
--- a/browser/components/urlbar/tests/ext/api.js
+++ b/browser/components/urlbar/tests/ext/api.js
@@ -5,11 +5,9 @@
 const { XPCOMUtils } = ChromeUtils.import(
   "resource://gre/modules/XPCOMUtils.jsm"
 );
-
 XPCOMUtils.defineLazyModuleGetters(this, {
   AppMenuNotifications: "resource://gre/modules/AppMenuNotifications.jsm",
   BrowserWindowTracker: "resource:///modules/BrowserWindowTracker.jsm",
-  ProfileAge: "resource://gre/modules/ProfileAge.jsm",
   Services: "resource://gre/modules/Services.jsm",
 });
 
@@ -108,19 +106,6 @@ this.experiments_urlbar = class extends ExtensionAPI {
             let errorCode = update ? update.errorCode : 0;
             return updateStateIs("pending") && errorCode != 0;
           },
-
-          async lastBrowserUpdateDate() {
-            // Get the newest update in the update history.  This isn't perfect
-            // because these dates are when updates are applied, not when the
-            // user restarts with the update.  See bug 1595328.
-            if (updateManager.updateCount) {
-              let update = updateManager.getUpdateAt(0);
-              return update.installDate;
-            }
-            // Fall back to the profile age.
-            let age = await ProfileAge();
-            return (await age.firstUse) || age.created;
-          },
         },
       },
     };
diff --git a/browser/components/urlbar/tests/ext/browser/browser.ini b/browser/components/urlbar/tests/ext/browser/browser.ini
index c8c16043fe7c..88b48bf5521e 100644
--- a/browser/components/urlbar/tests/ext/browser/browser.ini
+++ b/browser/components/urlbar/tests/ext/browser/browser.ini
@@ -11,4 +11,3 @@ support-files =
 
 [browser_ext_urlbar_isBrowserShowingNotification.js]
 [browser_ext_urlbar_isBrowserUpdateReadyToInstall.js]
-[browser_ext_urlbar_lastBrowserUpdateDate.js]
diff --git a/browser/components/urlbar/tests/ext/browser/browser_ext_urlbar_lastBrowserUpdateDate.js b/browser/components/urlbar/tests/ext/browser/browser_ext_urlbar_lastBrowserUpdateDate.js
deleted file mode 100644
index 43c7144b174c..000000000000
--- a/browser/components/urlbar/tests/ext/browser/browser_ext_urlbar_lastBrowserUpdateDate.js
+++ /dev/null
@@ -1,131 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
- * http://creativecommons.org/publicdomain/zero/1.0/ */
-
-/* global browser */
-
-// This tests the browser.experiments.urlbar.lastBrowserUpdateDate WebExtension
-// Experiment API.  The parts related to the updates.xml file are adapted from
-// browser_policy_override_postupdatepage.js and other similar tests.
-
-"use strict";
-
-XPCOMUtils.defineLazyModuleGetters(this, {
-  ProfileAge: "resource://gre/modules/ProfileAge.jsm",
-});
-
-XPCOMUtils.defineLazyServiceGetter(
-  this,
-  "updateManager",
-  "@mozilla.org/updates/update-manager;1",
-  "nsIUpdateManager"
-);
-
-const DATE_MS = 1368255600000;
-
-add_task(async function setUp() {
-  let originalTimes = (await ProfileAge())._times;
-  registerCleanupFunction(async () => {
-    removeUpdatesFile();
-    let age = await ProfileAge();
-    age._times = originalTimes;
-    await age.writeTimes();
-  });
-});
-
-// no update history, same profile created and first-use date
-add_task(async function noHistory_sameCreateAndFirstUse() {
-  removeUpdatesFile();
-  reloadUpdateManagerData();
-  Assert.equal(updateManager.updateCount, 0);
-  await updateProfileAge(DATE_MS, DATE_MS);
-  await checkExtension(DATE_MS);
-});
-
-// no update history, different profile created and first-use dates
-add_task(async function noHistory_differentCreateAndFirstUse() {
-  removeUpdatesFile();
-  reloadUpdateManagerData();
-  Assert.equal(updateManager.updateCount, 0);
-  await updateProfileAge(DATE_MS - 30000, DATE_MS);
-  await checkExtension(DATE_MS);
-});
-
-// update history
-add_task(async function history() {
-  removeUpdatesFile();
-  writeUpdatesFile(DATE_MS);
-  reloadUpdateManagerData();
-  Assert.equal(updateManager.updateCount, 1);
-  await updateProfileAge(DATE_MS - 60000, DATE_MS - 30000);
-  await checkExtension(DATE_MS);
-});
-
-async function checkExtension(expectedDate) {
-  let ext = await loadExtension(async () => {
-    let date = await browser.experiments.urlbar.lastBrowserUpdateDate();
-    browser.test.sendMessage("date", date);
-  });
-  let date = await ext.awaitMessage("date");
-  Assert.equal(date, expectedDate);
-  await ext.unload();
-}
-
-function getUpdatesFile() {
-  let updateRootDir = Services.dirsvc.get("UpdRootD", Ci.nsIFile);
-  let updatesFile = updateRootDir.clone();
-  updatesFile.append("updates.xml");
-  return updatesFile;
-}
-
-function removeUpdatesFile() {
-  try {
-    getUpdatesFile().remove(false);
-  } catch (e) {}
-}
-
-function reloadUpdateManagerData() {
-  updateManager
-    .QueryInterface(Ci.nsIObserver)
-    .observe(null, "um-reload-update-data", "");
-}
-
-function getUpdatesXML(installDate) {
-  return `<?xml version="1.0"?>
-  <updates xmlns="http://www.mozilla.org/2005/app-update">
-    <update appVersion="1.0" buildID="20080811053724" channel="nightly"
-            displayVersion="Version 1.0" installDate="${installDate}"
-            isCompleteUpdate="true" name="Update Test 1.0" type="minor"
-            detailsURL="http://example.com/" previousAppVersion="1.0"
-            serviceURL="https://example.com/"
-            statusText="The Update was successfully installed"
-            foregroundDownload="true">
-      <patch type="complete" URL="http://example.com/" size="775"
-             selected="true" state="succeeded"/>
-    </update>
-  </updates>`;
-}
-
-function writeUpdatesFile(installDate) {
-  const PERMS_FILE = 0o644;
-  const MODE_WRONLY = 0x02;
-  const MODE_CREATE = 0x08;
-  const MODE_TRUNCATE = 0x20;
-  let file = getUpdatesFile();
-  if (!file.exists()) {
-    file.create(Ci.nsIFile.NORMAL_FILE_TYPE, PERMS_FILE);
-  }
-  let fos = Cc["@mozilla.org/network/file-output-stream;1"].createInstance(
-    Ci.nsIFileOutputStream
-  );
-  let flags = MODE_WRONLY | MODE_CREATE | MODE_TRUNCATE;
-  fos.init(file, flags, PERMS_FILE, 0);
-  let xml = getUpdatesXML(installDate);
-  fos.write(xml, xml.length);
-  fos.close();
-}
-
-async function updateProfileAge(created, firstUse) {
-  let age = await ProfileAge();
-  age._times = { created, firstUse };
-  await age.writeTimes();
-}
diff --git a/browser/components/urlbar/tests/ext/schema.json b/browser/components/urlbar/tests/ext/schema.json
index c86ba2a78143..757f05ae1ccd 100644
--- a/browser/components/urlbar/tests/ext/schema.json
+++ b/browser/components/urlbar/tests/ext/schema.json
@@ -16,13 +16,6 @@
         "async": true,
         "description": "Returns true if there is an update ready to install.",
         "parameters": []
-      },
-      {
-        "name": "lastBrowserUpdateDate",
-        "type": "function",
-        "async": true,
-        "description": "Returns the date of the last browser update. If there's no update history, then the date the profile was first used is returned instead. The return value is milliseconds since 1 January 1970 UTC (i.e., suitable for passing to <code>new Date()</code>).",
-        "parameters": []
       }
     ]
   }