Allow user to set timezone (#12775)

* Allow user to set timezone

* Update test snapshots

---------

Co-authored-by: Florian Duros <florianduros@element.io>

test/TimezoneHandler-test.ts

@@ -0,0 +1,31 @@
+/*
+Copyright 2015, 2016 OpenMarket Ltd
+Copyright 2017 Vector Creations Ltd
+Copyright 2022 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import * as tzh from "../src/TimezoneHandler";
+
+describe("TimezoneHandler", () => {
+    it("should support setting a user timezone", async () => {
+        const tz = "Europe/Paris";
+        await tzh.setUserTimezone(tz);
+        expect(tzh.getUserTimezone()).toEqual(tz);
+    });
+    it("Return undefined with an empty TZ", async () => {
+        await tzh.setUserTimezone("");
+        expect(tzh.getUserTimezone()).toEqual(undefined);
+    });
+});