diff --git a/browser_patches/firefox/BUILD_NUMBER b/browser_patches/firefox/BUILD_NUMBER
index 69ed05c04b..373aef1ee5 100644
--- a/browser_patches/firefox/BUILD_NUMBER
+++ b/browser_patches/firefox/BUILD_NUMBER
@@ -1 +1 @@
-1063
+1064
diff --git a/browser_patches/firefox/patches/bootstrap.diff b/browser_patches/firefox/patches/bootstrap.diff
index 1ca65dd1a4..87281ebbce 100644
--- a/browser_patches/firefox/patches/bootstrap.diff
+++ b/browser_patches/firefox/patches/bootstrap.diff
@@ -138,15 +138,17 @@ index 040c7b124dec6bb254563bbe74fe50012cb077a3..b4e6b8132786af70e8ad0dce88b67c28
    const transportProvider = {
      setListener(upgradeListener) {
 diff --git a/docshell/base/nsDocShell.cpp b/docshell/base/nsDocShell.cpp
-index 514a4f2890a20558afe0d9c1aec697612fc8e873..44b48f306cb6c67264edbb2eaa49c890b657c675 100644
+index 514a4f2890a20558afe0d9c1aec697612fc8e873..4be480a4ec0e397c6c9a1d695a1faf381af414d1 100644
 --- a/docshell/base/nsDocShell.cpp
 +++ b/docshell/base/nsDocShell.cpp
-@@ -15,6 +15,12 @@
+@@ -15,6 +15,14 @@
  #  include <unistd.h>  // for getpid()
  #endif
  
 +#if JS_HAS_INTL_API && !MOZ_SYSTEM_ICU
 +#  include "unicode/locid.h"
++#  include "unicode/timezone.h"
++#  include "unicode/unistr.h"
 +#endif /* JS_HAS_INTL_API && !MOZ_SYSTEM_ICU */
 +
 +#include "js/LocaleSensitive.h"
@@ -154,7 +156,7 @@ index 514a4f2890a20558afe0d9c1aec697612fc8e873..44b48f306cb6c67264edbb2eaa49c890
  #include "mozilla/ArrayUtils.h"
  #include "mozilla/Attributes.h"
  #include "mozilla/AutoRestore.h"
-@@ -53,6 +59,7 @@
+@@ -53,6 +61,7 @@
  #include "mozilla/dom/ContentFrameMessageManager.h"
  #include "mozilla/dom/DocGroup.h"
  #include "mozilla/dom/Element.h"
@@ -162,7 +164,7 @@ index 514a4f2890a20558afe0d9c1aec697612fc8e873..44b48f306cb6c67264edbb2eaa49c890
  #include "mozilla/dom/HTMLAnchorElement.h"
  #include "mozilla/dom/PerformanceNavigation.h"
  #include "mozilla/dom/PermissionMessageUtils.h"
-@@ -71,6 +78,7 @@
+@@ -71,6 +80,7 @@
  #include "mozilla/dom/nsCSPContext.h"
  #include "mozilla/dom/LoadURIOptionsBinding.h"
  #include "mozilla/dom/JSWindowActorChild.h"
@@ -170,7 +172,7 @@ index 514a4f2890a20558afe0d9c1aec697612fc8e873..44b48f306cb6c67264edbb2eaa49c890
  
  #include "mozilla/net/DocumentChannel.h"
  #include "mozilla/net/DocumentChannelChild.h"
-@@ -96,6 +104,7 @@
+@@ -96,6 +106,7 @@
  #include "nsIDocShellTreeItem.h"
  #include "nsIDocShellTreeOwner.h"
  #include "mozilla/dom/Document.h"
@@ -178,7 +180,15 @@ index 514a4f2890a20558afe0d9c1aec697612fc8e873..44b48f306cb6c67264edbb2eaa49c890
  #include "nsIDocumentLoaderFactory.h"
  #include "nsIDOMWindow.h"
  #include "nsIEditingSession.h"
-@@ -350,6 +359,9 @@ nsDocShell::nsDocShell(BrowsingContext* aBrowsingContext,
+@@ -183,6 +194,7 @@
+ #include "nsGlobalWindow.h"
+ #include "nsISearchService.h"
+ #include "nsJSEnvironment.h"
++#include "nsJSUtils.h"
+ #include "nsNetCID.h"
+ #include "nsNetUtil.h"
+ #include "nsObjectLoadingContent.h"
+@@ -350,6 +362,9 @@ nsDocShell::nsDocShell(BrowsingContext* aBrowsingContext,
        mUseErrorPages(false),
        mObserveErrorPages(true),
        mCSSErrorReportingEnabled(false),
@@ -188,7 +198,7 @@ index 514a4f2890a20558afe0d9c1aec697612fc8e873..44b48f306cb6c67264edbb2eaa49c890
        mAllowAuth(mItemType == typeContent),
        mAllowKeywordFixup(false),
        mIsOffScreenBrowser(false),
-@@ -1219,6 +1231,7 @@ bool nsDocShell::SetCurrentURI(nsIURI* aURI, nsIRequest* aRequest,
+@@ -1219,6 +1234,7 @@ bool nsDocShell::SetCurrentURI(nsIURI* aURI, nsIRequest* aRequest,
      isSubFrame = mLSHE->GetIsSubFrame();
    }
  
@@ -196,7 +206,7 @@ index 514a4f2890a20558afe0d9c1aec697612fc8e873..44b48f306cb6c67264edbb2eaa49c890
    if (!isSubFrame && !isRoot) {
      /*
       * We don't want to send OnLocationChange notifications when
-@@ -3340,6 +3353,131 @@ nsDocShell::GetMessageManager(ContentFrameMessageManager** aMessageManager) {
+@@ -3340,6 +3356,162 @@ nsDocShell::GetMessageManager(ContentFrameMessageManager** aMessageManager) {
    return NS_OK;
  }
  
@@ -262,6 +272,37 @@ index 514a4f2890a20558afe0d9c1aec697612fc8e873..44b48f306cb6c67264edbb2eaa49c890
 +}
 +
 +NS_IMETHODIMP
++nsDocShell::OverrideTimezone(const nsAString& aTimezoneOverride, bool* aSuccess) {
++  NS_ENSURE_ARG(aSuccess);
++
++  // Validate timezone id.
++  UniquePtr<icu::TimeZone> timezone(icu::TimeZone::createTimeZone(
++      icu::UnicodeString(NS_LossyConvertUTF16toASCII(aTimezoneOverride).get(), -1, US_INV)));
++  if (!timezone || *timezone == icu::TimeZone::getUnknown()) {
++    fprintf(stderr, "Invalid timezone id: %s\n", NS_LossyConvertUTF16toASCII(aTimezoneOverride).get());
++    *aSuccess = false;
++    return NS_OK;
++  }
++
++  // The env variable is read by js::DateTimeInfo::internalResyncICUDefaultTimeZone()
++  auto setTimeZoneEnv = [](const char* value) {
++#if defined(_WIN32)
++    return _putenv_s("TZ", value) == 0;
++#else
++    return setenv("TZ", value, true) == 0;
++#endif /* _WIN32 */
++  };
++
++  *aSuccess = setTimeZoneEnv(NS_LossyConvertUTF16toASCII(aTimezoneOverride).get());
++  if (*aSuccess) {
++    nsJSUtils::ResetTimeZone();
++  } else {
++    fprintf(stderr, "Failed to change timezone to '%s'\n", NS_LossyConvertUTF16toASCII(aTimezoneOverride).get());
++  }
++  return NS_OK;
++}
++
++NS_IMETHODIMP
 +nsDocShell::GetFileInputInterceptionEnabled(bool* aEnabled) {
 +  MOZ_ASSERT(aEnabled);
 +  *aEnabled = GetRootDocShell()->mFileInputInterceptionEnabled;
@@ -328,7 +369,7 @@ index 514a4f2890a20558afe0d9c1aec697612fc8e873..44b48f306cb6c67264edbb2eaa49c890
  NS_IMETHODIMP
  nsDocShell::GetIsNavigating(bool* aOut) {
    *aOut = mIsNavigating;
-@@ -12137,6 +12275,9 @@ class OnLinkClickEvent : public Runnable {
+@@ -12137,6 +12309,9 @@ class OnLinkClickEvent : public Runnable {
                                  mNoOpenerImplied, nullptr, nullptr,
                                  mIsUserTriggered, mTriggeringPrincipal, mCsp);
      }
@@ -338,7 +379,7 @@ index 514a4f2890a20558afe0d9c1aec697612fc8e873..44b48f306cb6c67264edbb2eaa49c890
      return NS_OK;
    }
  
-@@ -12226,6 +12367,9 @@ nsresult nsDocShell::OnLinkClick(
+@@ -12226,6 +12401,9 @@ nsresult nsDocShell::OnLinkClick(
        this, aContent, aURI, target, aFileName, aPostDataStream,
        aHeadersDataStream, noOpenerImplied, aIsUserTriggered, aIsTrusted,
        aTriggeringPrincipal, aCsp);
@@ -405,7 +446,7 @@ index cc88045201371eb2195a28c60fcd3b6d940e8b72..7fad3529cc7a22b0b2aa8d8cb5ebbb58
    bool mAllowKeywordFixup : 1;
    bool mIsOffScreenBrowser : 1;
 diff --git a/docshell/base/nsIDocShell.idl b/docshell/base/nsIDocShell.idl
-index ee89208c3ada6da09ecda6147e1a372ee0562810..83a70dd59a22abd391f9b2db99837e3e5851db31 100644
+index ee89208c3ada6da09ecda6147e1a372ee0562810..ce8d31365b5190ac2c974100a6ec6408c53681d5 100644
 --- a/docshell/base/nsIDocShell.idl
 +++ b/docshell/base/nsIDocShell.idl
 @@ -44,6 +44,7 @@ interface nsIURI;
@@ -416,7 +457,7 @@ index ee89208c3ada6da09ecda6147e1a372ee0562810..83a70dd59a22abd391f9b2db99837e3e
  interface nsIDocShellLoadInfo;
  interface nsIEditor;
  interface nsIEditingSession;
-@@ -1129,4 +1130,19 @@ interface nsIDocShell : nsIDocShellTreeItem
+@@ -1129,4 +1130,21 @@ interface nsIDocShell : nsIDocShellTreeItem
     * @see nsISHEntry synchronizeLayoutHistoryState().
     */
    void synchronizeLayoutHistoryState();
@@ -427,6 +468,8 @@ index ee89208c3ada6da09ecda6147e1a372ee0562810..83a70dd59a22abd391f9b2db99837e3e
 +
 +  attribute AString languageOverride;
 +
++  boolean overrideTimezone(in AString timezoneId);
++
 +  cenum OnlineOverride: 8 {
 +    ONLINE_OVERRIDE_NONE = 0,
 +    ONLINE_OVERRIDE_ONLINE = 1,
@@ -1953,10 +1996,10 @@ index 0000000000000000000000000000000000000000..ba34976ad05e7f5f1a99777f76ac08b1
 +this.SimpleChannel = SimpleChannel;
 diff --git a/juggler/TargetRegistry.js b/juggler/TargetRegistry.js
 new file mode 100644
-index 0000000000000000000000000000000000000000..98d00f70a61787e31c5ae58310fd86312f3d0dcf
+index 0000000000000000000000000000000000000000..dcf03385589acc29c7fe0f02f912d40ab7efb76f
 --- /dev/null
 +++ b/juggler/TargetRegistry.js
-@@ -0,0 +1,471 @@
+@@ -0,0 +1,479 @@
 +const {EventEmitter} = ChromeUtils.import('resource://gre/modules/EventEmitter.jsm');
 +const {Helper} = ChromeUtils.import('chrome://juggler/content/Helper.js');
 +const {SimpleChannel} = ChromeUtils.import('chrome://juggler/content/SimpleChannel.js');
@@ -2048,6 +2091,10 @@ index 0000000000000000000000000000000000000000..98d00f70a61787e31c5ae58310fd8631
 +    this._mainWindow.gBrowser.selectedTab = tab;
 +    const target = this._tabToTarget.get(tab);
 +    await target._contentReadyPromise;
++    if (browserContext.options.timezoneId) {
++      if (await target.hasFailedToOverrideTimezone())
++        throw new Error('Failed to override timezone');
++    }
 +    return target.id();
 +  }
 +
@@ -2249,6 +2296,10 @@ index 0000000000000000000000000000000000000000..98d00f70a61787e31c5ae58310fd8631
 +    await this._channel.connect('').send('setOnlineOverride', override).catch(e => void e);
 +  }
 +
++  async hasFailedToOverrideTimezone() {
++    return await this._channel.connect('').send('hasFailedToOverrideTimezone').catch(e => true);
++  }
++
 +  dispose() {
 +    this._disposed = true;
 +    if (this._browserContext)
@@ -4840,10 +4891,10 @@ index 0000000000000000000000000000000000000000..3a386425d3796d0a6786dea193b3402d
 +
 diff --git a/juggler/content/main.js b/juggler/content/main.js
 new file mode 100644
-index 0000000000000000000000000000000000000000..b1f66264a97a0ca24fe29fb8a04e3ea2f5ec9eeb
+index 0000000000000000000000000000000000000000..1864328a47107621309c9b3726bb84535b780c2f
 --- /dev/null
 +++ b/juggler/content/main.js
-@@ -0,0 +1,146 @@
+@@ -0,0 +1,153 @@
 +const {Services} = ChromeUtils.import("resource://gre/modules/Services.jsm");
 +const {Helper} = ChromeUtils.import('chrome://juggler/content/Helper.js');
 +const {FrameTree} = ChromeUtils.import('chrome://juggler/content/content/FrameTree.js');
@@ -4908,8 +4959,11 @@ index 0000000000000000000000000000000000000000..b1f66264a97a0ca24fe29fb8a04e3ea2
 +    response = { sessionIds: [], browserContextOptions: {}, waitForInitialNavigation: false };
 +
 +  const { sessionIds, browserContextOptions, waitForInitialNavigation } = response;
-+  const { userAgent, bypassCSP, javaScriptDisabled, viewport, scriptsToEvaluateOnNewDocument, bindings, locale, geolocation, onlineOverride } = browserContextOptions;
++  const { userAgent, bypassCSP, javaScriptDisabled, viewport, scriptsToEvaluateOnNewDocument, bindings, locale, timezoneId, geolocation, onlineOverride } = browserContextOptions;
 +
++  let failedToOverrideTimezone = false;
++  if (timezoneId)
++    failedToOverrideTimezone = !docShell.overrideTimezone(timezoneId);
 +  if (userAgent !== undefined)
 +    docShell.browsingContext.customUserAgent = userAgent;
 +  if (bypassCSP !== undefined)
@@ -4970,6 +5024,10 @@ index 0000000000000000000000000000000000000000..b1f66264a97a0ca24fe29fb8a04e3ea2
 +      // noop, just a rountrip.
 +    },
 +
++    hasFailedToOverrideTimezone() {
++      return failedToOverrideTimezone;
++    },
++
 +    dispose() {
 +    },
 +  });
@@ -6075,10 +6133,10 @@ index 0000000000000000000000000000000000000000..78b6601b91d0b7fcda61114e6846aa07
 +this.EXPORTED_SYMBOLS = ['t', 'checkScheme'];
 diff --git a/juggler/protocol/Protocol.js b/juggler/protocol/Protocol.js
 new file mode 100644
-index 0000000000000000000000000000000000000000..67df4d5592d66e0db3c7c120ad12f9b360b9c45d
+index 0000000000000000000000000000000000000000..4028ed2f4c87e869da15103e936f85e887d769a1
 --- /dev/null
 +++ b/juggler/protocol/Protocol.js
-@@ -0,0 +1,778 @@
+@@ -0,0 +1,779 @@
 +const {t, checkScheme} = ChromeUtils.import('chrome://juggler/content/protocol/PrimitiveTypes.js');
 +
 +// Protocol-specific types.
@@ -6294,6 +6352,7 @@ index 0000000000000000000000000000000000000000..67df4d5592d66e0db3c7c120ad12f9b3
 +        javaScriptDisabled: t.Optional(t.Boolean),
 +        viewport: t.Optional(pageTypes.Viewport),
 +        locale: t.Optional(t.String),
++        timezoneId: t.Optional(t.String),
 +      },
 +      returns: {
 +        browserContextId: t.String,