From 3e3263b7b7eae6aebbe92c945bf9aa2553ee0255 Mon Sep 17 00:00:00 2001
From: Ilya Vinogradov <48182348+williamvinogradov@users.noreply.github.com>
Date: Tue, 12 Sep 2023 14:25:10 +0400
Subject: [PATCH] T1185479: Scheduler - Incorrect date shown for recurrence in
 the New Zealand timezone (#25531)

Co-authored-by: Ilya Vinogradov <ilya.vinogradov@devexpress.com>
---
 .../js/__internal/scheduler/m_recurrence.ts   | 39 ++++++++++++++++---
 packages/devextreme/js/core/utils/date.js     | 12 +++++-
 2 files changed, 44 insertions(+), 7 deletions(-)

diff --git a/packages/devextreme/js/__internal/scheduler/m_recurrence.ts b/packages/devextreme/js/__internal/scheduler/m_recurrence.ts
index c226d5229ad7..06149b9b0a26 100644
--- a/packages/devextreme/js/__internal/scheduler/m_recurrence.ts
+++ b/packages/devextreme/js/__internal/scheduler/m_recurrence.ts
@@ -17,6 +17,16 @@ const loggedWarnings: any = [];
 const MS_IN_HOUR = 1000 * 60 * 60;
 const MS_IN_DAY = MS_IN_HOUR * 24;
 
+const RRULE_BROKEN_TIMEZONES = [
+  'Etc/GMT-13',
+  'MIT',
+  'Pacific/Apia',
+  'Pacific/Enderbury',
+  'Pacific/Tongatapu',
+  'Etc/GMT-14',
+  'Pacific/Kiritimati',
+];
+
 let recurrence: RecurrenceProcessor | null = null;
 
 export function getRecurrenceProcessor() {
@@ -92,13 +102,8 @@ class RecurrenceProcessor {
   }
 
   _convertRruleResult(rruleIntervalParams, options, rruleDate) {
-    const localTimezoneOffset = timeZoneUtils.getClientTimezoneOffset(rruleDate);
-    // NOTE: Workaround for the RRule bug with timezones greater than GMT+12 (e.g. Apia Standard Time GMT+13)
-    // GitHub issue: https://github.com/jakubroztocil/rrule/issues/555
-    const additionalWorkaroundOffsetForRrule = localTimezoneOffset / MS_IN_HOUR <= -13 ? -MS_IN_DAY : 0;
     const convertedBackDate = timeZoneUtils.setOffsetsToDate(rruleDate, [
-      localTimezoneOffset,
-      additionalWorkaroundOffsetForRrule,
+      ...this._getLocalMachineOffset(rruleDate),
       -options.appointmentTimezoneOffset,
       rruleIntervalParams.startIntervalDateDSTShift,
     ]);
@@ -114,6 +119,28 @@ class RecurrenceProcessor {
     return resultDate;
   }
 
+  _getLocalMachineOffset(rruleDate) {
+    const machineTimezoneOffset = timeZoneUtils.getClientTimezoneOffset(rruleDate);
+    const machineTimezoneName = dateUtils.getMachineTimezoneName();
+    const result = [machineTimezoneOffset];
+
+    // NOTE: Workaround for the RRule bug with timezones greater than GMT+12 (e.g. Apia Standard Time GMT+13)
+    // GitHub issue: https://github.com/jakubroztocil/rrule/issues/555
+    // UPD: 05.09.2023 - The issue still hasn't been fixed in the Rule package.
+    // RRule returns results that are one day greater than expected.
+    // Therefore, for broken from RRule point of view timezones, we subtract one day from the result.
+    const brokenTimezonesOffset = -13;
+    const isTimezoneOffsetInBrokenRange = machineTimezoneOffset / MS_IN_HOUR <= brokenTimezonesOffset;
+    const isTimezoneNameInBrokenNames = !machineTimezoneName
+      || RRULE_BROKEN_TIMEZONES.some((timezone) => machineTimezoneName.includes(timezone));
+
+    if (isTimezoneOffsetInBrokenRange && isTimezoneNameInBrokenNames) {
+      result.push(-MS_IN_DAY);
+    }
+
+    return result;
+  }
+
   hasRecurrence(options) {
     return !!this.generateDates(options).length;
   }
diff --git a/packages/devextreme/js/core/utils/date.js b/packages/devextreme/js/core/utils/date.js
index 9988f56c0bff..0360cfa222ed 100644
--- a/packages/devextreme/js/core/utils/date.js
+++ b/packages/devextreme/js/core/utils/date.js
@@ -1,3 +1,4 @@
+/* globals Intl */
 import { isObject, isString, isDate, isDefined, isNumeric } from './type';
 import { adjust } from './math';
 import { each } from './iterator';
@@ -680,6 +681,13 @@ const createDateWithFullYear = function(year) {
     return result;
 };
 
+const getMachineTimezoneName = () => {
+    const hasIntl = typeof Intl !== 'undefined';
+    return hasIntl
+        ? Intl.DateTimeFormat().resolvedOptions().timeZone
+        : null;
+};
+
 const dateUtils = {
     dateUnitIntervals: dateUnitIntervals,
 
@@ -740,7 +748,9 @@ const dateUtils = {
 
     getDatesOfInterval: getDatesOfInterval,
 
-    createDateWithFullYear: createDateWithFullYear
+    createDateWithFullYear: createDateWithFullYear,
+
+    getMachineTimezoneName: getMachineTimezoneName,
 };
 
 dateUtils.sameView = function(view, date1, date2) {