Remove Intl polyfill on connection and consistently resolve time zone (#19326)

src/common/datetime/format_date.ts

@@ -1,7 +1,8 @@
 import { HassConfig } from "home-assistant-js-websocket";
 import memoizeOne from "memoize-one";
-import { FrontendLocaleData, DateFormat } from "../../data/translation";
+import { DateFormat, FrontendLocaleData } from "../../data/translation";
 import "../../resources/intl-polyfill";
+import { resolveTimeZone } from "./resolve-time-zone";
 
 // Tuesday, August 10
 export const formatDateWeekdayDay = (
@@ -16,7 +17,7 @@ const formatDateWeekdayDayMem = memoizeOne(
       weekday: "long",
       month: "long",
       day: "numeric",
-      timeZone: locale.time_zone === "server" ? serverTimeZone : undefined,
+      timeZone: resolveTimeZone(locale.time_zone, serverTimeZone),
     })
 );
 
@@ -33,7 +34,7 @@ const formatDateMem = memoizeOne(
       year: "numeric",
       month: "long",
       day: "numeric",
-      timeZone: locale.time_zone === "server" ? serverTimeZone : undefined,
+      timeZone: resolveTimeZone(locale.time_zone, serverTimeZone),
     })
 );
 
@@ -50,7 +51,7 @@ const formatDateShortMem = memoizeOne(
       year: "numeric",
       month: "short",
       day: "numeric",
-      timeZone: locale.time_zone === "server" ? serverTimeZone : undefined,
+      timeZone: resolveTimeZone(locale.time_zone, serverTimeZone),
     })
 );
 
@@ -105,7 +106,7 @@ const formatDateNumericMem = memoizeOne(
         year: "numeric",
         month: "numeric",
         day: "numeric",
-        timeZone: locale.time_zone === "server" ? serverTimeZone : undefined,
+        timeZone: resolveTimeZone(locale.time_zone, serverTimeZone),
       });
     }
 
@@ -113,7 +114,7 @@ const formatDateNumericMem = memoizeOne(
       year: "numeric",
       month: "numeric",
       day: "numeric",
-      timeZone: locale.time_zone === "server" ? serverTimeZone : undefined,
+      timeZone: resolveTimeZone(locale.time_zone, serverTimeZone),
     });
   }
 );
@@ -130,7 +131,7 @@ const formatDateVeryShortMem = memoizeOne(
     new Intl.DateTimeFormat(locale.language, {
       day: "numeric",
       month: "short",
-      timeZone: locale.time_zone === "server" ? serverTimeZone : undefined,
+      timeZone: resolveTimeZone(locale.time_zone, serverTimeZone),
     })
 );
 
@@ -146,7 +147,7 @@ const formatDateMonthYearMem = memoizeOne(
     new Intl.DateTimeFormat(locale.language, {
       month: "long",
       year: "numeric",
-      timeZone: locale.time_zone === "server" ? serverTimeZone : undefined,
+      timeZone: resolveTimeZone(locale.time_zone, serverTimeZone),
     })
 );
 
@@ -161,7 +162,7 @@ const formatDateMonthMem = memoizeOne(
   (locale: FrontendLocaleData, serverTimeZone: string) =>
     new Intl.DateTimeFormat(locale.language, {
       month: "long",
-      timeZone: locale.time_zone === "server" ? serverTimeZone : undefined,
+      timeZone: resolveTimeZone(locale.time_zone, serverTimeZone),
     })
 );
 
@@ -176,7 +177,7 @@ const formatDateYearMem = memoizeOne(
   (locale: FrontendLocaleData, serverTimeZone: string) =>
     new Intl.DateTimeFormat(locale.language, {
       year: "numeric",
-      timeZone: locale.time_zone === "server" ? serverTimeZone : undefined,
+      timeZone: resolveTimeZone(locale.time_zone, serverTimeZone),
     })
 );
 
@@ -191,7 +192,7 @@ const formatDateWeekdayMem = memoizeOne(
   (locale: FrontendLocaleData, serverTimeZone: string) =>
     new Intl.DateTimeFormat(locale.language, {
       weekday: "long",
-      timeZone: locale.time_zone === "server" ? serverTimeZone : undefined,
+      timeZone: resolveTimeZone(locale.time_zone, serverTimeZone),
     })
 );
 
@@ -206,6 +207,6 @@ const formatDateWeekdayShortMem = memoizeOne(
   (locale: FrontendLocaleData, serverTimeZone: string) =>
     new Intl.DateTimeFormat(locale.language, {
       weekday: "short",
-      timeZone: locale.time_zone === "server" ? serverTimeZone : undefined,
+      timeZone: resolveTimeZone(locale.time_zone, serverTimeZone),
     })
 );

src/common/datetime/format_date_time.ts

@@ -4,6 +4,7 @@ import { FrontendLocaleData } from "../../data/translation";
 import "../../resources/intl-polyfill";
 import { formatDateNumeric } from "./format_date";
 import { formatTime } from "./format_time";
+import { resolveTimeZone } from "./resolve-time-zone";
 import { useAmPm } from "./use_am_pm";
 
 // August 9, 2021, 8:23 AM
@@ -22,7 +23,7 @@ const formatDateTimeMem = memoizeOne(
       hour: useAmPm(locale) ? "numeric" : "2-digit",
       minute: "2-digit",
       hourCycle: useAmPm(locale) ? "h12" : "h23",
-      timeZone: locale.time_zone === "server" ? serverTimeZone : undefined,
+      timeZone: resolveTimeZone(locale.time_zone, serverTimeZone),
     })
 );
 
@@ -42,7 +43,7 @@ const formatShortDateTimeWithYearMem = memoizeOne(
       hour: useAmPm(locale) ? "numeric" : "2-digit",
       minute: "2-digit",
       hourCycle: useAmPm(locale) ? "h12" : "h23",
-      timeZone: locale.time_zone === "server" ? serverTimeZone : undefined,
+      timeZone: resolveTimeZone(locale.time_zone, serverTimeZone),
     })
 );
 
@@ -61,7 +62,7 @@ const formatShortDateTimeMem = memoizeOne(
       hour: useAmPm(locale) ? "numeric" : "2-digit",
       minute: "2-digit",
       hourCycle: useAmPm(locale) ? "h12" : "h23",
-      timeZone: locale.time_zone === "server" ? serverTimeZone : undefined,
+      timeZone: resolveTimeZone(locale.time_zone, serverTimeZone),
     })
 );
 
@@ -82,7 +83,7 @@ const formatDateTimeWithSecondsMem = memoizeOne(
       minute: "2-digit",
       second: "2-digit",
       hourCycle: useAmPm(locale) ? "h12" : "h23",
-      timeZone: locale.time_zone === "server" ? serverTimeZone : undefined,
+      timeZone: resolveTimeZone(locale.time_zone, serverTimeZone),
     })
 );
 

src/common/datetime/format_time.ts

@@ -2,6 +2,7 @@ import { HassConfig } from "home-assistant-js-websocket";
 import memoizeOne from "memoize-one";
 import { FrontendLocaleData } from "../../data/translation";
 import "../../resources/intl-polyfill";
+import { resolveTimeZone } from "./resolve-time-zone";
 import { useAmPm } from "./use_am_pm";
 
 // 9:15 PM || 21:15
@@ -17,7 +18,7 @@ const formatTimeMem = memoizeOne(
       hour: "numeric",
       minute: "2-digit",
       hourCycle: useAmPm(locale) ? "h12" : "h23",
-      timeZone: locale.time_zone === "server" ? serverTimeZone : undefined,
+      timeZone: resolveTimeZone(locale.time_zone, serverTimeZone),
     })
 );
 
@@ -35,7 +36,7 @@ const formatTimeWithSecondsMem = memoizeOne(
       minute: "2-digit",
       second: "2-digit",
       hourCycle: useAmPm(locale) ? "h12" : "h23",
-      timeZone: locale.time_zone === "server" ? serverTimeZone : undefined,
+      timeZone: resolveTimeZone(locale.time_zone, serverTimeZone),
     })
 );
 
@@ -53,7 +54,7 @@ const formatTimeWeekdayMem = memoizeOne(
       hour: useAmPm(locale) ? "numeric" : "2-digit",
       minute: "2-digit",
       hourCycle: useAmPm(locale) ? "h12" : "h23",
-      timeZone: locale.time_zone === "server" ? serverTimeZone : undefined,
+      timeZone: resolveTimeZone(locale.time_zone, serverTimeZone),
     })
 );
 
@@ -71,6 +72,6 @@ const formatTime24hMem = memoizeOne(
       hour: "numeric",
       minute: "2-digit",
       hour12: false,
-      timeZone: locale.time_zone === "server" ? serverTimeZone : undefined,
+      timeZone: resolveTimeZone(locale.time_zone, serverTimeZone),
     })
 );

src/common/datetime/localize_date.ts

@@ -1,4 +1,5 @@
 import memoizeOne from "memoize-one";
+import "../../resources/intl-polyfill";
 
 export const localizeWeekdays = memoizeOne(
   (language: string, short: boolean): string[] => {

src/common/datetime/resolve-time-zone.ts

@@ -0,0 +1,15 @@
+import { TimeZone } from "../../data/translation";
+
+// Browser  time zone can be determined from Intl, with fallback to UTC for polyfill or no support.
+// Alternatively, we could fallback to a fixed offset IANA zone (e.g. "Etc/GMT+5") using
+// Date.prototype.getTimeOffset(), but IANA only has whole hour Etc zones, and problems
+// might occur with relative time due to DST.
+// Use optional chain instead of polyfill import since polyfill will always return UTC
+export const LOCAL_TIME_ZONE =
+  Intl.DateTimeFormat?.().resolvedOptions?.().timeZone ?? "UTC";
+
+// Pick time zone based on user profile option.  Core zone is used when local cannot be determined.
+export const resolveTimeZone = (option: TimeZone, serverTimeZone: string) =>
+  option === TimeZone.local && LOCAL_TIME_ZONE !== "UTC"
+    ? LOCAL_TIME_ZONE
+    : serverTimeZone;

src/onboarding/onboarding-core-config.ts

@@ -9,6 +9,7 @@ import {
   TemplateResult,
 } from "lit";
 import { customElement, property, state } from "lit/decorators";
+import { LOCAL_TIME_ZONE } from "../common/datetime/resolve-time-zone";
 import { fireEvent } from "../common/dom/fire_event";
 import type { LocalizeFunc } from "../common/translations/localize";
 import "../components/ha-alert";
@@ -33,8 +34,7 @@ class OnboardingCoreConfig extends LitElement {
 
   private _elevation = "0";
 
-  private _timeZone: ConfigUpdateValues["time_zone"] =
-    Intl.DateTimeFormat?.().resolvedOptions?.().timeZone;
+  private _timeZone: ConfigUpdateValues["time_zone"] = LOCAL_TIME_ZONE;
 
   private _language: ConfigUpdateValues["language"] = getLocalLanguage();
 

src/panels/calendar/dialog-calendar-event-detail.ts

@@ -25,6 +25,7 @@ import { renderRRuleAsText } from "./recurrence";
 import { showConfirmEventDialog } from "./show-confirm-event-dialog-box";
 import { CalendarEventDetailDialogParams } from "./show-dialog-calendar-event-detail";
 import { showCalendarEventEditDialog } from "./show-dialog-calendar-event-editor";
+import { resolveTimeZone } from "../../common/datetime/resolve-time-zone";
 
 class DialogCalendarEventDetail extends LitElement {
   @property({ attribute: false }) public hass!: HomeAssistant;
@@ -138,8 +139,10 @@ class DialogCalendarEventDetail extends LitElement {
   }
 
   private _formatDateRange() {
-    // Parse a dates in the browser timezone
-    const timeZone = Intl.DateTimeFormat().resolvedOptions().timeZone;
+    const timeZone = resolveTimeZone(
+      this.hass.locale.time_zone,
+      this.hass.config.time_zone
+    );
     const start = toDate(this._data!.dtstart, { timeZone: timeZone });
     const endValue = toDate(this._data!.dtend, { timeZone: timeZone });
     // All day events should be displayed as a day earlier

src/panels/calendar/dialog-calendar-event-editor.ts

@@ -11,6 +11,7 @@ import { HassEntity } from "home-assistant-js-websocket";
 import { CSSResultGroup, LitElement, css, html, nothing } from "lit";
 import { customElement, property, state } from "lit/decorators";
 import memoizeOne from "memoize-one";
+import { resolveTimeZone } from "../../common/datetime/resolve-time-zone";
 import { fireEvent } from "../../common/dom/fire_event";
 import { computeStateDomain } from "../../common/entity/compute_state_domain";
 import { supportsFeature } from "../../common/entity/supports-feature";
@@ -32,7 +33,6 @@ import {
   deleteCalendarEvent,
   updateCalendarEvent,
 } from "../../data/calendar";
-import { TimeZone } from "../../data/translation";
 import { haStyleDialog } from "../../resources/styles";
 import { HomeAssistant } from "../../types";
 import "../lovelace/components/hui-generic-entity-row";
@@ -68,7 +68,7 @@ class DialogCalendarEventEditor extends LitElement {
 
   @state() private _submitting = false;
 
-  // Dates are manipulated and displayed in the browser timezone
+  // Dates are displayed in the timezone according to the user's profile
   // which may be different from the Home Assistant timezone. When
   // events are persisted, they are relative to the Home Assistant
   // timezone, but floating without a timezone.
@@ -85,10 +85,10 @@ class DialogCalendarEventEditor extends LitElement {
           computeStateDomain(stateObj) === "calendar" &&
           supportsFeature(stateObj, CalendarEntityFeature.CREATE_EVENT)
       )?.entity_id;
-    this._timeZone =
-      this.hass.locale.time_zone === TimeZone.local
-        ? Intl.DateTimeFormat().resolvedOptions().timeZone
-        : this.hass.config.time_zone;
+    this._timeZone = resolveTimeZone(
+      this.hass.locale.time_zone,
+      this.hass.config.time_zone
+    );
     if (params.entry) {
       const entry = params.entry!;
       this._allDay = isDate(entry.dtstart);

src/panels/config/core/ha-config-section-general.ts

@@ -294,10 +294,7 @@ class HaConfigSectionGeneral extends LitElement {
     this._country = this.hass.config.country;
     this._language = this.hass.config.language;
     this._elevation = this.hass.config.elevation;
-    this._timeZone =
-      this.hass.config.time_zone ||
-      Intl.DateTimeFormat?.().resolvedOptions?.().timeZone ||
-      "Etc/GMT";
+    this._timeZone = this.hass.config.time_zone || "Etc/GMT";
     this._name = this.hass.config.location_name;
     this._updateUnits = true;
   }

src/panels/profile/ha-pick-time-zone-row.ts

@@ -2,6 +2,7 @@ import "@material/mwc-list/mwc-list-item";
 import { html, LitElement, TemplateResult } from "lit";
 import { customElement, property } from "lit/decorators";
 import { formatDateTimeNumeric } from "../../common/datetime/format_date_time";
+import { resolveTimeZone } from "../../common/datetime/resolve-time-zone";
 import { fireEvent } from "../../common/dom/fire_event";
 import "../../components/ha-card";
 import "../../components/ha-select";
@@ -48,10 +49,9 @@ class TimeZoneRow extends LitElement {
                 >${this.hass.localize(
                   `ui.panel.profile.time_zone.options.${format}`,
                   {
-                    timezone: (format === "server"
-                      ? this.hass.config.time_zone
-                      : Intl.DateTimeFormat?.().resolvedOptions?.().timeZone ||
-                        ""
+                    timezone: resolveTimeZone(
+                      format,
+                      this.hass.config.time_zone
                     ).replace("_", " "),
                   }
                 )}</span

src/panels/todo/dialog-todo-item-editor.ts

@@ -3,6 +3,7 @@ import { formatInTimeZone, toDate } from "date-fns-tz";
 import { CSSResultGroup, LitElement, css, html, nothing } from "lit";
 import { customElement, property, state } from "lit/decorators";
 import memoizeOne from "memoize-one";
+import { resolveTimeZone } from "../../common/datetime/resolve-time-zone";
 import { fireEvent } from "../../common/dom/fire_event";
 import { supportsFeature } from "../../common/entity/supports-feature";
 import "../../components/ha-alert";
@@ -19,7 +20,6 @@ import {
   deleteItems,
   updateItem,
 } from "../../data/todo";
-import { TimeZone } from "../../data/translation";
 import { showConfirmationDialog } from "../../dialogs/generic/show-dialog-box";
 import { haStyleDialog } from "../../resources/styles";
 import { HomeAssistant } from "../../types";
@@ -54,10 +54,10 @@ class DialogTodoItemEditor extends LitElement {
   public showDialog(params: TodoItemEditDialogParams): void {
     this._error = undefined;
     this._params = params;
-    this._timeZone =
-      this.hass.locale.time_zone === TimeZone.local
-        ? Intl.DateTimeFormat().resolvedOptions().timeZone
-        : this.hass.config.time_zone;
+    this._timeZone = resolveTimeZone(
+      this.hass.locale.time_zone,
+      this.hass.config.time_zone
+    );
     if (params.item) {
       const entry = params.item;
       this._checked = entry.status === TodoItemStatus.Completed;

src/state/connection-mixin.ts

@@ -259,17 +259,7 @@ export const connectionMixin = <T extends Constructor<HassBaseEl>>(
         }
         this._updateHass({ areas });
       });
-      subscribeConfig(conn, (config) => {
-        if (this.hass?.config?.time_zone !== config.time_zone) {
-          import("../resources/intl-polyfill").then(() => {
-            if ("__setDefaultTimeZone" in Intl.DateTimeFormat) {
-              // @ts-ignore
-              Intl.DateTimeFormat.__setDefaultTimeZone(config.time_zone);
-            }
-          });
-        }
-        this._updateHass({ config });
-      });
+      subscribeConfig(conn, (config) => this._updateHass({ config }));
       subscribeServices(conn, (services) => this._updateHass({ services }));
       subscribePanels(conn, (panels) => this._updateHass({ panels }));
       subscribeFrontendUserData(conn, "core", (userData) =>