From 4fbe02dfe1b99c374ddeea3ecfea1d291bbbc7d0 Mon Sep 17 00:00:00 2001
From: Maksim Zakharov <251575087+bit-byte0@users.noreply.github.com>
Date: Thu, 4 Jun 2026 15:58:36 +0400
Subject: [PATCH 1/9] refactor(scheduler): rename m_utils and m_utils_time_zone
 (drop m_ prefix)

---
 .../scheduler/__tests__/performance.test.ts   |   2 +-
 .../scheduler/appointment_popup/form.ts       |   2 +-
 .../appointments/m_appointment_collection.ts  |   2 +-
 .../js/__internal/scheduler/m_scheduler.ts    |   4 +-
 .../js/__internal/scheduler/m_subscribes.ts   |   2 +-
 .../js/__internal/scheduler/m_utils.ts        |  42 ---
 .../__internal/scheduler/m_utils_time_zone.ts | 290 ------------------
 .../scheduler/r1/timezone_calculator/utils.ts |   2 +-
 .../js/__internal/scheduler/r1/utils/base.ts  |   2 +-
 .../scheduler/recurrence/generate_dates.ts    |   2 +-
 .../scheduler_options_base_widget.ts          |   2 +-
 ...st.ts => utils_time_zone.santiago.test.ts} |   2 +-
 ...e_zone.test.ts => utils_time_zone.test.ts} |   2 +-
 .../get_date_information.ts                   |   2 +-
 .../options/get_minutes_cell_intervals.ts     |   2 +-
 .../view_model/get_appointment_info.ts        |   2 +-
 .../scheduler/workspaces/m_work_space.ts      |   2 +-
 .../scheduler/workspaces/timeline.ts          |   2 +-
 .../m_date_header_data_generator.ts           |   2 +-
 .../view_model/m_grouped_data_map_provider.ts |   2 +-
 .../view_model/m_view_data_generator.ts       |   2 +-
 .../view_model/m_view_data_generator_month.ts |   2 +-
 .../m_view_data_generator_timeline_month.ts   |   2 +-
 .../view_model/m_view_data_provider.ts        |   2 +-
 .../workspaces/work_space_indicator.ts        |   2 +-
 .../scheduler/workspaces/work_space_month.ts  |   2 +-
 .../common.methods.tests.js                   |   2 +-
 .../dataSource.tests.js                       |   2 +-
 .../integration.appointmentsVertical.tests.js |   2 +-
 .../timezones.tests.js                        |   2 +-
 30 files changed, 29 insertions(+), 361 deletions(-)
 delete mode 100644 packages/devextreme/js/__internal/scheduler/m_utils.ts
 delete mode 100644 packages/devextreme/js/__internal/scheduler/m_utils_time_zone.ts
 rename packages/devextreme/js/__internal/scheduler/{m_utils_time_zone.santiago.test.ts => utils_time_zone.santiago.test.ts} (92%)
 rename packages/devextreme/js/__internal/scheduler/{m_utils_time_zone.test.ts => utils_time_zone.test.ts} (98%)

diff --git a/packages/devextreme/js/__internal/scheduler/__tests__/performance.test.ts b/packages/devextreme/js/__internal/scheduler/__tests__/performance.test.ts
index dc13c5c5cf5d..92b1b4ecffda 100644
--- a/packages/devextreme/js/__internal/scheduler/__tests__/performance.test.ts
+++ b/packages/devextreme/js/__internal/scheduler/__tests__/performance.test.ts
@@ -2,7 +2,7 @@ import {
   beforeEach, describe, expect, it, jest,
 } from '@jest/globals';
 
-import timezoneUtils from '../m_utils_time_zone';
+import timezoneUtils from '../utils_time_zone';
 import { createScheduler } from './__mock__/create_scheduler';
 
 const startDate = new Date(2025, 0, 6);
diff --git a/packages/devextreme/js/__internal/scheduler/appointment_popup/form.ts b/packages/devextreme/js/__internal/scheduler/appointment_popup/form.ts
index 600e72ed09cc..2b5526acff2d 100644
--- a/packages/devextreme/js/__internal/scheduler/appointment_popup/form.ts
+++ b/packages/devextreme/js/__internal/scheduler/appointment_popup/form.ts
@@ -27,7 +27,6 @@ import { dateSerialization } from '@ts/core/utils/m_date_serialization';
 import DropDownEditor from '@ts/ui/drop_down_editor/drop_down_editor';
 import type Popup from '@ts/ui/popup/m_popup';
 
-import timeZoneUtils from '../m_utils_time_zone';
 import type { TimeZoneCalculator } from '../r1/timezone_calculator/calculator';
 import type { CreateComponentFn, SafeAppointment } from '../types';
 import type { AppointmentDataAccessor } from '../utils/data_accessor/appointment_data_accessor';
@@ -35,6 +34,7 @@ import type { ResourceLoader } from '../utils/loader/resource_loader';
 import { DEFAULT_ICONS_SHOW_MODE } from '../utils/options/constants';
 import { getAppointmentGroupIndex, getRawAppointmentGroupValues, getSafeGroupValues } from '../utils/resource_manager/appointment_groups_utils';
 import type { ResourceManager } from '../utils/resource_manager/resource_manager';
+import timeZoneUtils from '../utils_time_zone';
 import { customizeFormItems } from './customize_form_items';
 import { getRepeatSelectItems, REPEAT_NEVER_VALUE } from './localized_items';
 import type { AppointmentPopupContext } from './popup';
diff --git a/packages/devextreme/js/__internal/scheduler/appointments/m_appointment_collection.ts b/packages/devextreme/js/__internal/scheduler/appointments/m_appointment_collection.ts
index a85011fc3c0a..a27cab8d43dd 100644
--- a/packages/devextreme/js/__internal/scheduler/appointments/m_appointment_collection.ts
+++ b/packages/devextreme/js/__internal/scheduler/appointments/m_appointment_collection.ts
@@ -27,7 +27,7 @@ import {
   APPOINTMENT_ITEM_CLASS,
 } from '../classes';
 import { APPOINTMENT_SETTINGS_KEY } from '../constants';
-import timeZoneUtils from '../m_utils_time_zone';
+import timeZoneUtils from '../utils_time_zone';
 import type { CompactAppointmentOptions } from '../types';
 import { AppointmentAdapter } from '../utils/appointment_adapter/appointment_adapter';
 import type { AppointmentDataAccessor } from '../utils/data_accessor/appointment_data_accessor';
diff --git a/packages/devextreme/js/__internal/scheduler/m_scheduler.ts b/packages/devextreme/js/__internal/scheduler/m_scheduler.ts
index 2cfd65ffa81c..9f6c5c7d607c 100644
--- a/packages/devextreme/js/__internal/scheduler/m_scheduler.ts
+++ b/packages/devextreme/js/__internal/scheduler/m_scheduler.ts
@@ -51,8 +51,6 @@ import { hide as hideLoading, show as showLoading } from './loading';
 import { CompactAppointmentsHelper } from './m_compact_appointments_helper';
 import type { SubscribeKey, SubscribeMethods } from './m_subscribes';
 import subscribes from './m_subscribes';
-import { utils } from './m_utils';
-import timeZoneUtils, { type TimezoneLabel } from './m_utils_time_zone';
 import { combineRemoteFilter } from './r1/filterting/remote';
 import { createTimeZoneCalculator } from './r1/timezone_calculator/index';
 import {
@@ -73,6 +71,7 @@ import type {
   ScrollToGroupValuesOrOptions, ScrollToOptions, TargetedAppointment,
   ViewType,
 } from './types';
+import { utils } from './utils';
 import { AppointmentAdapter } from './utils/appointment_adapter/appointment_adapter';
 import { AppointmentDataAccessor } from './utils/data_accessor/appointment_data_accessor';
 import { getTargetedAppointment } from './utils/get_targeted_appointment';
@@ -83,6 +82,7 @@ import { VIEWS } from './utils/options/constants_view';
 import type { NormalizedView, SafeSchedulerOptions } from './utils/options/types';
 import { getAppointmentGroupValues, setAppointmentGroupValues } from './utils/resource_manager/appointment_groups_utils';
 import { ResourceManager } from './utils/resource_manager/resource_manager';
+import timeZoneUtils, { type TimezoneLabel } from './utils_time_zone';
 import AppointmentLayoutManager from './view_model/appointments_layout_manager';
 import { AppointmentDataSource } from './view_model/m_appointment_data_source';
 import type { AppointmentViewModelPlain } from './view_model/types';
diff --git a/packages/devextreme/js/__internal/scheduler/m_subscribes.ts b/packages/devextreme/js/__internal/scheduler/m_subscribes.ts
index d530559a8b82..6170ead29c8d 100644
--- a/packages/devextreme/js/__internal/scheduler/m_subscribes.ts
+++ b/packages/devextreme/js/__internal/scheduler/m_subscribes.ts
@@ -8,7 +8,6 @@ import { getDeltaTime } from './appointments/resizing/get_delta_time';
 import { getDateFormatType, getDateText } from './appointments_new/utils/get_date_text';
 import { VERTICAL_VIEW_TYPES } from './constants';
 import type Scheduler from './m_scheduler';
-import { utils } from './m_utils';
 import { isAppointmentTakesAllDay } from './r1/utils/base';
 import type {
   AppointmentTooltipItem,
@@ -16,6 +15,7 @@ import type {
   SafeAppointment,
   TargetedAppointment,
 } from './types';
+import { utils } from './utils';
 import { AppointmentAdapter } from './utils/appointment_adapter/appointment_adapter';
 import type { AppointmentItemViewModel } from './view_model/types';
 
diff --git a/packages/devextreme/js/__internal/scheduler/m_utils.ts b/packages/devextreme/js/__internal/scheduler/m_utils.ts
deleted file mode 100644
index 5ec2aa60830c..000000000000
--- a/packages/devextreme/js/__internal/scheduler/m_utils.ts
+++ /dev/null
@@ -1,42 +0,0 @@
-import { getPublicElement } from '@js/core/element';
-import $ from '@js/core/renderer';
-import { getOuterHeight, setHeight, setWidth } from '@js/core/utils/size';
-
-import { APPOINTMENT_SETTINGS_KEY } from './constants';
-import type { AppointmentViewModelPlain } from './view_model/types';
-
-export const utils = {
-  dataAccessors: {
-    getAppointmentSettings: (element) => $(element)
-      .data(APPOINTMENT_SETTINGS_KEY) as unknown as AppointmentViewModelPlain | undefined,
-  },
-  DOM: {
-    getHeaderHeight: (header) => (header
-      ? header._$element && parseInt(getOuterHeight(header._$element), 10)
-      : 0),
-  },
-  renovation: {
-    renderComponent: (widget, parentElement, componentClass, componentName, viewModel) => {
-      let component = widget[componentName];
-      if (!component) {
-        const container = getPublicElement(parentElement);
-        component = widget._createComponent(container, componentClass, viewModel);
-        widget[componentName] = component;
-      } else {
-        const $element = component.$element();
-        const elementStyle = $element.get(0).style;
-        const { height } = elementStyle;
-        const { width } = elementStyle;
-
-        component.option(viewModel);
-
-        if (height) {
-          setHeight($element, height);
-        }
-        if (width) {
-          setWidth($element, width);
-        }
-      }
-    },
-  },
-};
diff --git a/packages/devextreme/js/__internal/scheduler/m_utils_time_zone.ts b/packages/devextreme/js/__internal/scheduler/m_utils_time_zone.ts
deleted file mode 100644
index c704c975c414..000000000000
--- a/packages/devextreme/js/__internal/scheduler/m_utils_time_zone.ts
+++ /dev/null
@@ -1,290 +0,0 @@
-// TODO(Refactoring): move this module to ./utils directory
-import errors from '@js/core/errors';
-import { dateUtilsTs } from '@ts/core/utils/date';
-import { macroTaskArray } from '@ts/scheduler/utils/index';
-
-import dateUtils from '../../core/utils/date';
-import { globalCache } from './global_cache';
-import timeZoneList from './timezones/timezone_list';
-
-export interface TimezoneLabel {
-  /** uniq timezone id, e.g: 'America/Los_Angeles' */
-  id: string;
-  /** timezone display string, e.g: '(GMT -08:00) America - Los Angeles' */
-  title?: string;
-}
-
-export interface TimezoneData extends TimezoneLabel {
-  /** timezone offset in hours */
-  offset?: number;
-}
-
-const timeZoneListSet = new Set(timeZoneList.value);
-const toMs = dateUtils.dateToMilliseconds;
-const MINUTES_IN_HOUR = 60;
-const MS_IN_MINUTE = 60000;
-const GMT = 'GMT';
-const offsetFormatRegexp = /^GMT(?:[+-]\d{2}:\d{2})?$/;
-
-const createUTCDateWithLocalOffset = (date) => {
-  if (!date) {
-    return date;
-  }
-
-  return new Date(Date.UTC(
-    date.getFullYear(),
-    date.getMonth(),
-    date.getDate(),
-    date.getHours(),
-    date.getMinutes(),
-    date.getSeconds(),
-  ));
-};
-
-const createDateFromUTCWithLocalOffset = (date: Date): Date => new Date(
-  date.getUTCFullYear(),
-  date.getUTCMonth(),
-  date.getUTCDate(),
-  date.getUTCHours(),
-  date.getUTCMinutes(),
-  date.getUTCSeconds(),
-);
-
-const getTimezoneOffsetChangeInMinutes = (startDate, endDate, updatedStartDate, updatedEndDate) => getDaylightOffset(updatedStartDate, updatedEndDate) - getDaylightOffset(startDate, endDate);
-
-const getTimezoneOffsetChangeInMs = (startDate, endDate, updatedStartDate, updatedEndDate) => getTimezoneOffsetChangeInMinutes(startDate, endDate, updatedStartDate, updatedEndDate) * toMs('minute');
-
-const getDaylightOffset = (startDate, endDate) => new Date(startDate).getTimezoneOffset() - new Date(endDate).getTimezoneOffset();
-
-const getDaylightOffsetInMs = (startDate, endDate) => getDaylightOffset(startDate, endDate) * toMs('minute');
-
-const calculateTimezoneByValueCore = (timeZone: string, date = new Date()): number | undefined => {
-  const offset = getStringOffset(timeZone, date);
-
-  if (offset === undefined) {
-    return undefined;
-  }
-
-  if (offset === GMT) {
-    return 0;
-  }
-
-  const isMinus = offset.substring(3, 4) === '-';
-  const hours = offset.substring(4, 6);
-  const minutes = offset.substring(7, 9);
-
-  const result = parseInt(hours, 10) + parseInt(minutes, 10) / MINUTES_IN_HOUR;
-  return isMinus ? -result : result;
-};
-
-const calculateTimezoneByValue = (timeZone: string | undefined, date: Date | number = new Date()): number | undefined => {
-  if (!timeZone) {
-    return undefined;
-  }
-
-  const isValidTimezone = timeZoneListSet.has(timeZone);
-  if (!isValidTimezone) {
-    errors.log('W0009', timeZone);
-    return undefined;
-  }
-
-  const dateObj = new Date(date);
-  if (!dateUtilsTs.isValidDate(dateObj)) {
-    return undefined;
-  }
-
-  if (isEqualLocalTimeZone(timeZone)) {
-    return -dateObj.getTimezoneOffset() / MINUTES_IN_HOUR;
-  }
-
-  return calculateTimezoneByValueCore(timeZone, dateObj);
-};
-
-// 'GMT±XX:YY' or 'GMT' format
-const getStringOffset = (timeZone: string, date = new Date()): string | undefined => {
-  let result = '';
-  try {
-    const dateTimeFormat = globalCache.timezones.memo(`intl${timeZone}`, () => new Intl.DateTimeFormat('en-US', {
-      timeZone,
-      timeZoneName: 'longOffset',
-    }));
-
-    result = dateTimeFormat
-      .formatToParts(date)
-      .find(({ type }) => type === 'timeZoneName')?.value ?? '';
-  } catch (e) {
-    errors.log('W0009', timeZone);
-    return undefined;
-  }
-
-  const isSupportedFormat = offsetFormatRegexp.test(result);
-  if (!isSupportedFormat) {
-    errors.log('W0009', timeZone);
-    return undefined;
-  }
-
-  return result;
-};
-
-const getOffsetNamePart = (offset: string): string => {
-  if (offset === GMT) {
-    return `${offset} +00:00`;
-  }
-
-  return offset.replace(GMT, `${GMT} `);
-};
-
-const getTimezoneTitle = (timeZone: string, date = new Date()): string | undefined => {
-  if (!dateUtilsTs.isValidDate(date)) {
-    return '';
-  }
-
-  const tzNamePart = timeZone.replace(/\//g, ' - ').replace(/_/g, ' ');
-  const offset = getStringOffset(timeZone, date);
-  if (offset === undefined) {
-    return undefined;
-  }
-
-  const offsetNamePart = getOffsetNamePart(offset);
-  return `(${offsetNamePart}) ${tzNamePart}`;
-};
-
-// eslint-disable-next-line @typescript-eslint/naming-convention
-const _getDaylightOffsetByTimezone = (startDate: Date, endDate: Date, timeZone: string): number => {
-  const startDayOffset = calculateTimezoneByValue(timeZone, startDate);
-  const endDayOffset = calculateTimezoneByValue(timeZone, endDate);
-  if (startDayOffset === undefined || endDayOffset === undefined) {
-    return 0;
-  }
-
-  return startDayOffset - endDayOffset;
-};
-
-const getCorrectedDateByDaylightOffsets = (convertedOriginalStartDate, convertedDate, date, timeZone, startDateTimezone) => {
-  const daylightOffsetByCommonTimezone = _getDaylightOffsetByTimezone(convertedOriginalStartDate, convertedDate, timeZone);
-  const daylightOffsetByAppointmentTimezone = _getDaylightOffsetByTimezone(convertedOriginalStartDate, convertedDate, startDateTimezone);
-  const diff = daylightOffsetByCommonTimezone - daylightOffsetByAppointmentTimezone;
-
-  return new Date(date.getTime() - diff * toMs('hour'));
-};
-
-const correctRecurrenceExceptionByTimezone = (exception, exceptionByStartDate) => {
-  const timezoneOffset = (exception.getTimezoneOffset() - exceptionByStartDate.getTimezoneOffset()) / MINUTES_IN_HOUR;
-
-  return new Date(exception.getTime() + timezoneOffset * toMs('hour'));
-};
-
-const isTimezoneChangeInDate = (date) => {
-  const startDayDate = new Date(new Date(date).setHours(0, 0, 0, 0));
-  const endDayDate = new Date(new Date(date).setHours(23, 59, 59, 0));
-  return (startDayDate.getTimezoneOffset() - endDayDate.getTimezoneOffset()) !== 0;
-};
-
-const getDateWithoutTimezoneChange = (date) => {
-  const clonedDate = new Date(date);
-  if (isTimezoneChangeInDate(clonedDate)) {
-    const result = new Date(clonedDate);
-    return new Date(result.setDate(result.getDate() + 1));
-  }
-  return clonedDate;
-};
-
-const isSameAppointmentDates = (startDate, endDate) => {
-  // NOTE: subtract 1 millisecond to avoid 00.00 time. Method should return 'true' for "2020:10:10 22:00:00" and "2020:10:11 00:00:00", for example.
-  endDate = new Date(endDate.getTime() - 1);
-
-  return dateUtils.sameDate(startDate, endDate);
-};
-
-const getClientTimezoneOffset = (date = new Date()) => date.getTimezoneOffset() * MS_IN_MINUTE;
-
-const getDiffBetweenClientTimezoneOffsets = (firstDate = new Date(), secondDate = new Date()) => getClientTimezoneOffset(firstDate) - getClientTimezoneOffset(secondDate);
-
-const getMachineTimezoneName = () => globalCache.timezones.memo('localTimezone', () => dateUtils.getMachineTimezoneName());
-
-const isEqualLocalTimeZone = (timeZoneName: string) => {
-  const localTimeZoneName = getMachineTimezoneName();
-  if (localTimeZoneName && localTimeZoneName === timeZoneName) {
-    return true;
-  }
-  return false;
-};
-
-const addOffsetsWithoutDST = (date: Date, ...offsets: number[]): Date => {
-  const newDate = dateUtilsTs.addOffsets(date, ...offsets);
-  const daylightShift = getDaylightOffsetInMs(date, newDate);
-
-  if (!daylightShift) {
-    return newDate;
-  }
-
-  const correctLocalDate = dateUtilsTs.addOffsets(newDate, -daylightShift);
-  const daylightSecondShift = getDaylightOffsetInMs(newDate, correctLocalDate);
-
-  return !daylightSecondShift
-    ? correctLocalDate
-    : newDate;
-};
-
-const getTimeZones = (
-  date = new Date(),
-  timeZones = timeZoneList.value,
-): TimezoneData[] => timeZones.map((timezoneId) => ({
-  id: timezoneId,
-  title: getTimezoneTitle(timezoneId, date),
-  offset: calculateTimezoneByValue(timezoneId, date),
-}));
-
-const GET_TIMEZONES_BATCH_SIZE = 10;
-const cacheTimeZones = async (): Promise<TimezoneLabel[]> => globalCache.timezones.memo(
-  'timeZonesCachePromise',
-  () => macroTaskArray
-    .map(
-      timeZoneList.value,
-      (timezoneId) => ({
-        id: timezoneId,
-        title: getTimezoneTitle(timezoneId, new Date()),
-      }),
-      GET_TIMEZONES_BATCH_SIZE,
-    )
-    .then((data) => globalCache.timezones.memo('timeZonesCache', () => data)),
-);
-
-const getTimeZonesCache = (): TimezoneLabel[] => globalCache.timezones.get('timeZonesCache') ?? [];
-
-const isLocalTimeMidnightDST = (date: Date): boolean => {
-  const startDayDate = new Date(date.getFullYear(), date.getMonth(), date.getDate());
-
-  return startDayDate.getHours() === 1;
-};
-
-const utils = {
-  getDaylightOffset,
-  getDaylightOffsetInMs,
-  getTimezoneOffsetChangeInMinutes,
-  getTimezoneOffsetChangeInMs,
-  calculateTimezoneByValue,
-  getCorrectedDateByDaylightOffsets,
-  isSameAppointmentDates,
-  correctRecurrenceExceptionByTimezone,
-  getClientTimezoneOffset,
-  getDiffBetweenClientTimezoneOffsets,
-
-  createUTCDateWithLocalOffset,
-  createDateFromUTCWithLocalOffset,
-
-  isTimezoneChangeInDate,
-  getDateWithoutTimezoneChange,
-  getMachineTimezoneName,
-  isEqualLocalTimeZone,
-
-  addOffsetsWithoutDST,
-
-  getTimeZones,
-  getTimeZonesCache,
-  cacheTimeZones,
-
-  isLocalTimeMidnightDST,
-};
-
-export default utils;
diff --git a/packages/devextreme/js/__internal/scheduler/r1/timezone_calculator/utils.ts b/packages/devextreme/js/__internal/scheduler/r1/timezone_calculator/utils.ts
index 9b5c4c591a1c..84f12b39bf0e 100644
--- a/packages/devextreme/js/__internal/scheduler/r1/timezone_calculator/utils.ts
+++ b/packages/devextreme/js/__internal/scheduler/r1/timezone_calculator/utils.ts
@@ -1,4 +1,4 @@
-import timeZoneUtils from '../../m_utils_time_zone';
+import timeZoneUtils from '../../utils_time_zone';
 import { TimeZoneCalculator } from './calculator';
 
 export const createTimeZoneCalculator = (
diff --git a/packages/devextreme/js/__internal/scheduler/r1/utils/base.ts b/packages/devextreme/js/__internal/scheduler/r1/utils/base.ts
index 607d19165a82..bcb7457a933d 100644
--- a/packages/devextreme/js/__internal/scheduler/r1/utils/base.ts
+++ b/packages/devextreme/js/__internal/scheduler/r1/utils/base.ts
@@ -7,7 +7,7 @@ import { VERTICAL_GROUP_COUNT_CLASSES } from '../../classes';
 import {
   HORIZONTAL_GROUP_ORIENTATION, VERTICAL_GROUP_ORIENTATION,
 } from '../../constants';
-import timeZoneUtils from '../../m_utils_time_zone';
+import timeZoneUtils from '../../utils_time_zone';
 import type {
   AllDayPanelModeType,
   AppointmentGeometry,
diff --git a/packages/devextreme/js/__internal/scheduler/recurrence/generate_dates.ts b/packages/devextreme/js/__internal/scheduler/recurrence/generate_dates.ts
index 6027f03aa3ba..c5bc3f7fc390 100644
--- a/packages/devextreme/js/__internal/scheduler/recurrence/generate_dates.ts
+++ b/packages/devextreme/js/__internal/scheduler/recurrence/generate_dates.ts
@@ -1,7 +1,7 @@
 import { dateUtilsTs } from '@ts/core/utils/date';
 import { RRule, RRuleSet } from 'rrule';
 
-import timeZoneUtils from '../m_utils_time_zone';
+import timeZoneUtils from '../utils_time_zone';
 import { getDateByAsciiString, parseRecurrenceRule } from './base';
 import type { ProcessorOptions, RRuleParams } from './types';
 import { validateRRuleObject } from './validate_rule';
diff --git a/packages/devextreme/js/__internal/scheduler/scheduler_options_base_widget.ts b/packages/devextreme/js/__internal/scheduler/scheduler_options_base_widget.ts
index 50300301227e..b36e1c45741b 100644
--- a/packages/devextreme/js/__internal/scheduler/scheduler_options_base_widget.ts
+++ b/packages/devextreme/js/__internal/scheduler/scheduler_options_base_widget.ts
@@ -1,7 +1,6 @@
 import Widget from '@js/ui/widget/ui.widget';
 import { extend } from '@ts/core/utils/m_extend';
 
-import timeZoneUtils from './m_utils_time_zone';
 import {
   DEFAULT_SCHEDULER_INTEGRATION_OPTIONS,
   DEFAULT_SCHEDULER_INTERNAL_OPTIONS,
@@ -15,6 +14,7 @@ import type {
 } from './utils/options/types';
 import { getCurrentView, getViewOption, getViews } from './utils/options/utils';
 import { SchedulerOptionsValidator, SchedulerOptionsValidatorErrorsHandler } from './utils/options_validator/index';
+import timeZoneUtils from './utils_time_zone';
 
 export class SchedulerOptionsBaseWidget extends Widget<SafeSchedulerOptions> {
   protected views: NormalizedView[] = [];
diff --git a/packages/devextreme/js/__internal/scheduler/m_utils_time_zone.santiago.test.ts b/packages/devextreme/js/__internal/scheduler/utils_time_zone.santiago.test.ts
similarity index 92%
rename from packages/devextreme/js/__internal/scheduler/m_utils_time_zone.santiago.test.ts
rename to packages/devextreme/js/__internal/scheduler/utils_time_zone.santiago.test.ts
index 8563d2bab873..354709f51445 100644
--- a/packages/devextreme/js/__internal/scheduler/m_utils_time_zone.santiago.test.ts
+++ b/packages/devextreme/js/__internal/scheduler/utils_time_zone.santiago.test.ts
@@ -6,7 +6,7 @@ import {
   describe, expect, it,
 } from '@jest/globals';
 
-import timeZoneUtils from './m_utils_time_zone';
+import timeZoneUtils from './utils_time_zone';
 
 describe('isLocalTimeMidnightDST', () => {
   it('should return false for summer DST', () => {
diff --git a/packages/devextreme/js/__internal/scheduler/m_utils_time_zone.test.ts b/packages/devextreme/js/__internal/scheduler/utils_time_zone.test.ts
similarity index 98%
rename from packages/devextreme/js/__internal/scheduler/m_utils_time_zone.test.ts
rename to packages/devextreme/js/__internal/scheduler/utils_time_zone.test.ts
index bacd710c2525..acc54ae684d6 100644
--- a/packages/devextreme/js/__internal/scheduler/m_utils_time_zone.test.ts
+++ b/packages/devextreme/js/__internal/scheduler/utils_time_zone.test.ts
@@ -4,8 +4,8 @@ import {
 import { macroTaskArray } from '@ts/scheduler/utils/index';
 
 import { globalCache } from './global_cache';
-import timeZoneUtils from './m_utils_time_zone';
 import timeZoneList from './timezones/timezone_list';
+import timeZoneUtils from './utils_time_zone';
 
 const defaultTimeZones = timeZoneList.value;
 
diff --git a/packages/devextreme/js/__internal/scheduler/view_model/filtration/utils/split_by_recurrence/get_date_information.ts b/packages/devextreme/js/__internal/scheduler/view_model/filtration/utils/split_by_recurrence/get_date_information.ts
index 35281af8cdb7..4ee6edc62e5e 100644
--- a/packages/devextreme/js/__internal/scheduler/view_model/filtration/utils/split_by_recurrence/get_date_information.ts
+++ b/packages/devextreme/js/__internal/scheduler/view_model/filtration/utils/split_by_recurrence/get_date_information.ts
@@ -1,7 +1,7 @@
 import dateUtils from '@js/core/utils/date';
 
 import { globalCache } from '../../../../global_cache';
-import timeZoneUtils from '../../../../m_utils_time_zone';
+import timeZoneUtils from '../../../../utils_time_zone';
 
 export interface DateInformation {
   offsetMs: number;
diff --git a/packages/devextreme/js/__internal/scheduler/view_model/generate_view_model/options/get_minutes_cell_intervals.ts b/packages/devextreme/js/__internal/scheduler/view_model/generate_view_model/options/get_minutes_cell_intervals.ts
index 6085f47c2afe..dc4b1b31bcc6 100644
--- a/packages/devextreme/js/__internal/scheduler/view_model/generate_view_model/options/get_minutes_cell_intervals.ts
+++ b/packages/devextreme/js/__internal/scheduler/view_model/generate_view_model/options/get_minutes_cell_intervals.ts
@@ -1,6 +1,6 @@
 import { dateUtils } from '@ts/core/utils/m_date';
 
-import timeZoneUtils from '../../../m_utils_time_zone';
+import timeZoneUtils from '../../../utils_time_zone';
 import { splitIntervalByDay } from '../../common/split_interval_by_days';
 import type { CellInterval, DateInterval } from '../../types';
 
diff --git a/packages/devextreme/js/__internal/scheduler/view_model/get_appointment_info.ts b/packages/devextreme/js/__internal/scheduler/view_model/get_appointment_info.ts
index 58e8c9ccc3d4..6d59ecba0bf3 100644
--- a/packages/devextreme/js/__internal/scheduler/view_model/get_appointment_info.ts
+++ b/packages/devextreme/js/__internal/scheduler/view_model/get_appointment_info.ts
@@ -1,4 +1,4 @@
-import timeZoneUtils from '../m_utils_time_zone';
+import timeZoneUtils from '../utils_time_zone';
 import type {
   AppointmentAgendaViewModel,
   AppointmentItemViewModel,
diff --git a/packages/devextreme/js/__internal/scheduler/workspaces/m_work_space.ts b/packages/devextreme/js/__internal/scheduler/workspaces/m_work_space.ts
index aa83e0941532..59438594a231 100644
--- a/packages/devextreme/js/__internal/scheduler/workspaces/m_work_space.ts
+++ b/packages/devextreme/js/__internal/scheduler/workspaces/m_work_space.ts
@@ -73,7 +73,7 @@ import AppointmentDragBehavior from '../m_appointment_drag_behavior';
 import { CompactAppointmentsHelper } from '../m_compact_appointments_helper';
 import type { SubscribeKey, SubscribeMethods } from '../m_subscribes';
 import tableCreatorModule, { type GroupRows } from '../m_table_creator';
-import { utils } from '../m_utils';
+import { utils } from '../utils';
 import VerticalShader from '../shaders/current_time_shader_vertical';
 import type { ViewCellData } from '../types';
 import type { ResourceLoader } from '../utils/loader/resource_loader';
diff --git a/packages/devextreme/js/__internal/scheduler/workspaces/timeline.ts b/packages/devextreme/js/__internal/scheduler/workspaces/timeline.ts
index aec079d7d622..4aa823777848 100644
--- a/packages/devextreme/js/__internal/scheduler/workspaces/timeline.ts
+++ b/packages/devextreme/js/__internal/scheduler/workspaces/timeline.ts
@@ -17,7 +17,7 @@ import {
   GROUP_ROW_CLASS,
 } from '../classes';
 import tableCreatorModule, { type GroupRows } from '../m_table_creator';
-import timezoneUtils from '../m_utils_time_zone';
+import timezoneUtils from '../utils_time_zone';
 import HorizontalShader from '../shaders/current_time_shader_horizontal';
 import type { ResourceLoader } from '../utils/loader/resource_loader';
 import { getFirstVisibleDate } from '../utils/skipped_days';
diff --git a/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_date_header_data_generator.ts b/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_date_header_data_generator.ts
index 8cd05ceb7e50..fa54720943b1 100644
--- a/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_date_header_data_generator.ts
+++ b/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_date_header_data_generator.ts
@@ -1,7 +1,6 @@
 import dateUtils from '@js/core/utils/date';
 import type { DateHeaderData } from '@ts/scheduler/types';
 
-import timeZoneUtils from '../../m_utils_time_zone';
 import {
   formatWeekdayAndDay,
   getDisplayedCellCount,
@@ -11,6 +10,7 @@ import {
   isTimelineView,
 } from '../../r1/utils/index';
 import { VIEWS } from '../../utils/options/constants_view';
+import timeZoneUtils from '../../utils_time_zone';
 import type { ViewDataProviderExtendedOptions } from './m_types';
 
 export class DateHeaderDataGenerator {
diff --git a/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_grouped_data_map_provider.ts b/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_grouped_data_map_provider.ts
index af60dd63d2b4..a5e1f1ebe012 100644
--- a/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_grouped_data_map_provider.ts
+++ b/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_grouped_data_map_provider.ts
@@ -2,7 +2,7 @@ import dateUtils from '@js/core/utils/date';
 import { dateUtilsTs } from '@ts/core/utils/date';
 import { isDateAndTimeView } from '@ts/scheduler/r1/utils/index';
 
-import timezoneUtils from '../../m_utils_time_zone';
+import timezoneUtils from '../../utils_time_zone';
 
 const toMs = dateUtils.dateToMilliseconds;
 
diff --git a/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_view_data_generator.ts b/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_view_data_generator.ts
index c853f48e82ed..2b96bb2333e8 100644
--- a/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_view_data_generator.ts
+++ b/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_view_data_generator.ts
@@ -3,7 +3,6 @@ import { dateUtilsTs } from '@ts/core/utils/date';
 import type { GroupLeaf } from '@ts/scheduler/utils/resource_manager/types';
 
 import { HORIZONTAL_GROUP_ORIENTATION } from '../../constants';
-import timezoneUtils from '../../m_utils_time_zone';
 import {
   calculateCellIndex,
   calculateDayDuration,
@@ -22,6 +21,7 @@ import {
   getVisibleDaysOfWeek,
   isDateSkipped,
 } from '../../utils/skipped_days';
+import timezoneUtils from '../../utils_time_zone';
 import type {
   ViewCellDataSimple,
   ViewCellGeneratedData,
diff --git a/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_view_data_generator_month.ts b/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_view_data_generator_month.ts
index 9f979cfa05b1..6370e2dfdc69 100644
--- a/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_view_data_generator_month.ts
+++ b/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_view_data_generator_month.ts
@@ -4,7 +4,7 @@ import {
   getToday, isFirstCellInMonthWithIntervalCount, monthUtils, setOptionHour,
 } from '@ts/scheduler/r1/utils/index';
 
-import timezoneUtils from '../../m_utils_time_zone';
+import timezoneUtils from '../../utils_time_zone';
 import type { MonthViewCellDataSimple, ViewDataProviderExtendedOptions } from './m_types';
 import { ViewDataGenerator } from './m_view_data_generator';
 import { calculateAlignedWeeksBetweenDates } from './utils/view_generator_utils';
diff --git a/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_view_data_generator_timeline_month.ts b/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_view_data_generator_timeline_month.ts
index 56a45bd5fd49..f85d5720b3b4 100644
--- a/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_view_data_generator_timeline_month.ts
+++ b/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_view_data_generator_timeline_month.ts
@@ -1,8 +1,8 @@
 import dateUtils from '@js/core/utils/date';
 import { setOptionHour, timelineMonthUtils } from '@ts/scheduler/r1/utils/index';
 
-import timezoneUtils from '../../m_utils_time_zone';
 import type { CountGenerationConfig } from '../../types';
+import timezoneUtils from '../../utils_time_zone';
 import { ViewDataGenerator } from './m_view_data_generator';
 
 const toMs = dateUtils.dateToMilliseconds;
diff --git a/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_view_data_provider.ts b/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_view_data_provider.ts
index 1189212f074b..d384bbe4016e 100644
--- a/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_view_data_provider.ts
+++ b/packages/devextreme/js/__internal/scheduler/workspaces/view_model/m_view_data_provider.ts
@@ -1,7 +1,6 @@
 import dateUtils from '@js/core/utils/date';
 import { dateUtilsTs } from '@ts/core/utils/date';
 
-import timeZoneUtils from '../../m_utils_time_zone';
 import {
   calculateIsGroupedAllDayPanel,
   getGroupPanelData,
@@ -18,6 +17,7 @@ import type {
   ViewDataMap, ViewOptions,
   ViewType,
 } from '../../types';
+import timeZoneUtils from '../../utils_time_zone';
 import { DateHeaderDataGenerator } from './m_date_header_data_generator';
 import { GroupedDataMapProvider } from './m_grouped_data_map_provider';
 import { TimePanelDataGenerator } from './m_time_panel_data_generator';
diff --git a/packages/devextreme/js/__internal/scheduler/workspaces/work_space_indicator.ts b/packages/devextreme/js/__internal/scheduler/workspaces/work_space_indicator.ts
index ea640311efaf..f16304fb5f15 100644
--- a/packages/devextreme/js/__internal/scheduler/workspaces/work_space_indicator.ts
+++ b/packages/devextreme/js/__internal/scheduler/workspaces/work_space_indicator.ts
@@ -10,7 +10,7 @@ import type { OptionChanged } from '@ts/core/widget/types';
 import { getToday } from '@ts/scheduler/r1/utils/index';
 
 import { HEADER_CURRENT_TIME_CELL_CLASS } from '../classes';
-import timezoneUtils from '../m_utils_time_zone';
+import timezoneUtils from '../utils_time_zone';
 import SchedulerWorkSpace, {
   type WorkspaceOptionsInternal,
 } from './m_work_space';
diff --git a/packages/devextreme/js/__internal/scheduler/workspaces/work_space_month.ts b/packages/devextreme/js/__internal/scheduler/workspaces/work_space_month.ts
index b0b81f198bb8..b66a259fecd4 100644
--- a/packages/devextreme/js/__internal/scheduler/workspaces/work_space_month.ts
+++ b/packages/devextreme/js/__internal/scheduler/workspaces/work_space_month.ts
@@ -6,7 +6,7 @@ import { hasWindow } from '@js/core/utils/window';
 import { DateTableMonthComponent } from '@ts/scheduler/r1/components/index';
 import { formatWeekday, monthUtils } from '@ts/scheduler/r1/utils/index';
 
-import { utils } from '../m_utils';
+import { utils } from '../utils';
 import { VIEWS } from '../utils/options/constants_view';
 import type { ViewDateGenerationOptions } from './m_work_space';
 import SchedulerWorkSpace from './work_space_indicator';
diff --git a/packages/devextreme/testing/tests/DevExpress.ui.widgets.scheduler/common.methods.tests.js b/packages/devextreme/testing/tests/DevExpress.ui.widgets.scheduler/common.methods.tests.js
index fd3d36810fd9..1da239c9ff7a 100644
--- a/packages/devextreme/testing/tests/DevExpress.ui.widgets.scheduler/common.methods.tests.js
+++ b/packages/devextreme/testing/tests/DevExpress.ui.widgets.scheduler/common.methods.tests.js
@@ -3,7 +3,7 @@ import fx from 'common/core/animation/fx';
 import { CustomStore } from 'common/data/custom_store';
 import { DataSource } from 'common/data/data_source/data_source';
 
-import timeZoneUtils from '__internal/scheduler/m_utils_time_zone';
+import timeZoneUtils from '__internal/scheduler/utils_time_zone';
 import { createWrapper, initTestMarkup } from '../../helpers/scheduler/helpers.js';
 import { waitAsync } from '../../helpers/scheduler/waitForAsync.js';
 
diff --git a/packages/devextreme/testing/tests/DevExpress.ui.widgets.scheduler/dataSource.tests.js b/packages/devextreme/testing/tests/DevExpress.ui.widgets.scheduler/dataSource.tests.js
index a3855bc24824..22e59ce8282b 100644
--- a/packages/devextreme/testing/tests/DevExpress.ui.widgets.scheduler/dataSource.tests.js
+++ b/packages/devextreme/testing/tests/DevExpress.ui.widgets.scheduler/dataSource.tests.js
@@ -9,7 +9,7 @@ import { DataSource } from 'common/data/data_source/data_source';
 import ArrayStore from 'common/data/array_store';
 import fx from 'common/core/animation/fx';
 import translator from 'common/core/animation/translator';
-import timeZoneUtils from '__internal/scheduler/m_utils_time_zone';
+import timeZoneUtils from '__internal/scheduler/utils_time_zone';
 import { CustomStore } from 'common/data/custom_store';
 import { noop } from 'core/utils/common';
 import dragEvents from 'common/core/events/drag';
diff --git a/packages/devextreme/testing/tests/DevExpress.ui.widgets.scheduler/integration.appointmentsVertical.tests.js b/packages/devextreme/testing/tests/DevExpress.ui.widgets.scheduler/integration.appointmentsVertical.tests.js
index ab8112ea4ca0..ebd4b857083d 100644
--- a/packages/devextreme/testing/tests/DevExpress.ui.widgets.scheduler/integration.appointmentsVertical.tests.js
+++ b/packages/devextreme/testing/tests/DevExpress.ui.widgets.scheduler/integration.appointmentsVertical.tests.js
@@ -7,7 +7,7 @@ import translator from 'common/core/animation/translator';
 import fx from 'common/core/animation/fx';
 import { DataSource } from 'common/data/data_source/data_source';
 import dataUtils from 'core/element_data';
-import timeZoneUtils from '__internal/scheduler/m_utils_time_zone';
+import timeZoneUtils from '__internal/scheduler/utils_time_zone';
 
 import 'fluent_blue_light.css!';
 import '__internal/scheduler/m_scheduler';
diff --git a/packages/devextreme/testing/tests/DevExpress.ui.widgets.scheduler/timezones.tests.js b/packages/devextreme/testing/tests/DevExpress.ui.widgets.scheduler/timezones.tests.js
index de564fc47ced..a73405cbba06 100644
--- a/packages/devextreme/testing/tests/DevExpress.ui.widgets.scheduler/timezones.tests.js
+++ b/packages/devextreme/testing/tests/DevExpress.ui.widgets.scheduler/timezones.tests.js
@@ -16,7 +16,7 @@ import { hide } from '__internal/ui/tooltip/m_tooltip';
 import { DataSource } from 'common/data/data_source/data_source';
 import ArrayStore from 'common/data/array_store';
 import dragEvents from 'common/core/events/drag';
-import timeZoneUtils from '__internal/scheduler/m_utils_time_zone';
+import timeZoneUtils from '__internal/scheduler/utils_time_zone';
 
 import 'fluent_blue_light.css!';
 

From 940b483c9b7642c933205a51f0c5be8f8202e393 Mon Sep 17 00:00:00 2001
From: Maksim Zakharov <251575087+bit-byte0@users.noreply.github.com>
Date: Thu, 4 Jun 2026 16:44:32 +0400
Subject: [PATCH 2/9] refactor(scheduler): rename m_utils and m_utils_time_zone

---
 .../scheduler/r1/utils/agenda.pacific.test.ts |   8 +-
 .../r1/utils/agenda.santiago.test.ts          |   8 +-
 .../__internal/scheduler/r1/utils/agenda.ts   |   5 +-
 .../js/__internal/scheduler/utils.ts          |  73 ++++
 .../__internal/scheduler/utils_time_zone.ts   | 349 ++++++++++++++++++
 .../view_model/common/get_compare_options.ts  |   6 +-
 .../steps/virtual_screen_filter.ts            |   6 +-
 7 files changed, 439 insertions(+), 16 deletions(-)
 create mode 100644 packages/devextreme/js/__internal/scheduler/utils.ts
 create mode 100644 packages/devextreme/js/__internal/scheduler/utils_time_zone.ts

diff --git a/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.pacific.test.ts b/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.pacific.test.ts
index b208afc7fbb9..221ec0c810cf 100644
--- a/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.pacific.test.ts
+++ b/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.pacific.test.ts
@@ -4,14 +4,14 @@
 
 import { describe, expect, it } from '@jest/globals';
 
-import timeZoneUtils from '../../m_utils_time_zone';
+import timeZoneUtils from '../../utils_time_zone';
 import { calculateRows } from './agenda';
 
 const createDate = (year: number, month: number, day: number, hours: number) => {
-  const dateUTC = timeZoneUtils.createUTCDateWithLocalOffset(
+  const date = timeZoneUtils.createUTCDateWithLocalOffset(
     new Date(year, month, day, hours),
-  ).getTime();
-  return dateUTC;
+  );
+  return date ? date.getTime() : 0;
 };
 
 describe('calculateRows', () => {
diff --git a/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.santiago.test.ts b/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.santiago.test.ts
index 23f42e32ea0e..5c9a66868afb 100644
--- a/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.santiago.test.ts
+++ b/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.santiago.test.ts
@@ -4,14 +4,14 @@
 
 import { describe, expect, it } from '@jest/globals';
 
-import timeZoneUtils from '../../m_utils_time_zone';
+import timeZoneUtils from '../../utils_time_zone';
 import { calculateRows } from './agenda';
 
 const createDate = (year: number, month: number, day: number, hours: number) => {
-  const dateUTC = timeZoneUtils.createUTCDateWithLocalOffset(
+  const date = timeZoneUtils.createUTCDateWithLocalOffset(
     new Date(year, month, day, hours),
-  ).getTime();
-  return dateUTC;
+  );
+  return date ? date.getTime() : 0;
 };
 
 describe('calculateRows', () => {
diff --git a/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.ts b/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.ts
index c6d475fd17dd..04143ef0adc8 100644
--- a/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.ts
+++ b/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.ts
@@ -1,4 +1,4 @@
-import timeZoneUtils from '../../m_utils_time_zone';
+import timeZoneUtils from '../../utils_time_zone';
 import type { ListEntity } from '../../view_model/types';
 import { setOptionHour } from './base';
 
@@ -49,7 +49,8 @@ export const calculateRows = (
 
   for (let i = 0; i < agendaDuration; i += 1) {
     const date = getDateByIndex(startViewDate, i);
-    const dayStart = getDayStart(timeZoneUtils.createUTCDateWithLocalOffset(date));
+    const utcDate = timeZoneUtils.createUTCDateWithLocalOffset(date);
+    const dayStart = getDayStart(utcDate as Date);
     intervalsStartMap.set(dayStart, i);
   }
 
diff --git a/packages/devextreme/js/__internal/scheduler/utils.ts b/packages/devextreme/js/__internal/scheduler/utils.ts
new file mode 100644
index 000000000000..3fd18943717e
--- /dev/null
+++ b/packages/devextreme/js/__internal/scheduler/utils.ts
@@ -0,0 +1,73 @@
+import { getPublicElement } from '@js/core/element';
+import type { dxElementWrapper } from '@js/core/renderer';
+import $ from '@js/core/renderer';
+import { getOuterHeight, setHeight, setWidth } from '@js/core/utils/size';
+
+import { APPOINTMENT_SETTINGS_KEY } from './constants';
+import type { AppointmentViewModelPlain } from './view_model/types';
+
+interface HeaderWithElement {
+  [key: string]: unknown;
+}
+
+interface RenovationWidget {
+  [key: string]: unknown;
+}
+
+export const utils = {
+  dataAccessors: {
+    getAppointmentSettings: (
+      element: Element,
+    ): AppointmentViewModelPlain | undefined => $(element)
+      .data(APPOINTMENT_SETTINGS_KEY) as unknown as AppointmentViewModelPlain | undefined,
+  },
+  DOM: {
+    getHeaderHeight: (
+      header: HeaderWithElement | null | undefined,
+    ): number => {
+      const $element = header?._$element as
+        dxElementWrapper | undefined;
+      return $element
+        ? parseInt(getOuterHeight($element), 10)
+        : 0;
+    },
+  },
+  renovation: {
+    renderComponent: (
+      widget: RenovationWidget,
+      parentElement: dxElementWrapper,
+      componentClass: unknown,
+      componentName: string,
+      viewModel: Record<string, unknown>,
+    ): void => {
+      let component = widget[componentName] as
+        Record<string, Function> | undefined;
+      if (!component) {
+        const container = getPublicElement(parentElement);
+        const createComponent = widget._createComponent as
+          Function;
+        component = createComponent(
+          container,
+          componentClass,
+          viewModel,
+        ) as Record<string, Function>;
+        widget[componentName] = component;
+      } else {
+        const $element = component.$element() as
+          dxElementWrapper;
+        const elementStyle = ($element.get(0) as HTMLElement).style;
+        const { height } = elementStyle;
+        const { width } = elementStyle;
+
+        (component.option)(viewModel);
+
+        if (height) {
+          setHeight($element, height);
+        }
+        if (width) {
+          setWidth($element, width);
+        }
+      }
+    },
+  },
+};
diff --git a/packages/devextreme/js/__internal/scheduler/utils_time_zone.ts b/packages/devextreme/js/__internal/scheduler/utils_time_zone.ts
new file mode 100644
index 000000000000..ca4dff2d6c41
--- /dev/null
+++ b/packages/devextreme/js/__internal/scheduler/utils_time_zone.ts
@@ -0,0 +1,349 @@
+// TODO(Refactoring): move this module to ./utils directory
+import errors from '@js/core/errors';
+import { dateUtilsTs } from '@ts/core/utils/date';
+import { macroTaskArray } from '@ts/scheduler/utils/index';
+
+import dateUtils from '../../core/utils/date';
+import { globalCache } from './global_cache';
+import timeZoneList from './timezones/timezone_list';
+
+export interface TimezoneLabel {
+  /** uniq timezone id, e.g: 'America/Los_Angeles' */
+  id: string;
+  /** timezone display string, e.g: '(GMT -08:00) America - Los Angeles' */
+  title?: string;
+}
+
+export interface TimezoneData extends TimezoneLabel {
+  /** timezone offset in hours */
+  offset?: number;
+}
+
+const timeZoneListSet = new Set(timeZoneList.value);
+const toMs = dateUtils.dateToMilliseconds;
+const MINUTES_IN_HOUR = 60;
+const MS_IN_MINUTE = 60000;
+const GMT = 'GMT';
+const offsetFormatRegexp = /^GMT(?:[+-]\d{2}:\d{2})?$/;
+
+const createUTCDateWithLocalOffset = (date: Date | null | undefined): Date | null | undefined => {
+  if (!date) {
+    return date;
+  }
+
+  return new Date(Date.UTC(
+    date.getFullYear(),
+    date.getMonth(),
+    date.getDate(),
+    date.getHours(),
+    date.getMinutes(),
+    date.getSeconds(),
+  ));
+};
+
+const createDateFromUTCWithLocalOffset = (date: Date): Date => new Date(
+  date.getUTCFullYear(),
+  date.getUTCMonth(),
+  date.getUTCDate(),
+  date.getUTCHours(),
+  date.getUTCMinutes(),
+  date.getUTCSeconds(),
+);
+
+const getDaylightOffset = (
+  startDate: Date | number,
+  endDate: Date | number,
+): number => new Date(startDate).getTimezoneOffset() - new Date(endDate).getTimezoneOffset();
+
+const getDaylightOffsetInMs = (
+  startDate: Date | number,
+  endDate: Date | number,
+): number => getDaylightOffset(startDate, endDate) * toMs('minute');
+
+const getTimezoneOffsetChangeInMinutes = (
+  startDate: Date,
+  endDate: Date,
+  updatedStartDate: Date,
+  updatedEndDate: Date,
+): number => getDaylightOffset(updatedStartDate, updatedEndDate) - getDaylightOffset(
+  startDate,
+  endDate,
+);
+
+const getTimezoneOffsetChangeInMs = (
+  startDate: Date,
+  endDate: Date,
+  updatedStartDate: Date,
+  updatedEndDate: Date,
+): number => {
+  const minutes = getTimezoneOffsetChangeInMinutes(
+    startDate,
+    endDate,
+    updatedStartDate,
+    updatedEndDate,
+  );
+  return minutes * toMs('minute');
+};
+
+// 'GMT±XX:YY' or 'GMT' format
+const getStringOffset = (timeZone: string, date = new Date()): string | undefined => {
+  let result = '';
+  try {
+    const dateTimeFormat = globalCache.timezones.memo(
+      `intl${timeZone}`,
+      () => new Intl.DateTimeFormat('en-US', {
+        timeZone,
+        timeZoneName: 'longOffset',
+      }),
+    );
+
+    result = dateTimeFormat
+      .formatToParts(date)
+      .find(({ type }) => type === 'timeZoneName')?.value ?? '';
+  } catch (e) {
+    errors.log('W0009', timeZone);
+    return undefined;
+  }
+
+  const isSupportedFormat = offsetFormatRegexp.test(result);
+  if (!isSupportedFormat) {
+    errors.log('W0009', timeZone);
+    return undefined;
+  }
+
+  return result;
+};
+
+const calculateTimezoneByValueCore = (timeZone: string, date = new Date()): number | undefined => {
+  const offset = getStringOffset(timeZone, date);
+
+  if (offset === undefined) {
+    return undefined;
+  }
+
+  if (offset === GMT) {
+    return 0;
+  }
+
+  const isMinus = offset.substring(3, 4) === '-';
+  const hours = offset.substring(4, 6);
+  const minutes = offset.substring(7, 9);
+
+  const result = parseInt(hours, 10) + parseInt(minutes, 10) / MINUTES_IN_HOUR;
+  return isMinus ? -result : result;
+};
+
+const getMachineTimezoneName = (): string | null => globalCache.timezones.memo(
+  'localTimezone',
+  () => dateUtils.getMachineTimezoneName(),
+);
+
+const isEqualLocalTimeZone = (timeZoneName: string): boolean => {
+  const localTimeZoneName = getMachineTimezoneName();
+  if (localTimeZoneName && localTimeZoneName === timeZoneName) {
+    return true;
+  }
+  return false;
+};
+
+const calculateTimezoneByValue = (
+  timeZone: string | undefined,
+  date: Date | number = new Date(),
+): number | undefined => {
+  if (!timeZone) {
+    return undefined;
+  }
+
+  const isValidTimezone = timeZoneListSet.has(timeZone);
+  if (!isValidTimezone) {
+    errors.log('W0009', timeZone);
+    return undefined;
+  }
+
+  const dateObj = new Date(date);
+  if (!dateUtilsTs.isValidDate(dateObj)) {
+    return undefined;
+  }
+
+  if (isEqualLocalTimeZone(timeZone)) {
+    return -dateObj.getTimezoneOffset() / MINUTES_IN_HOUR;
+  }
+
+  return calculateTimezoneByValueCore(timeZone, dateObj);
+};
+
+const getOffsetNamePart = (offset: string): string => {
+  if (offset === GMT) {
+    return `${offset} +00:00`;
+  }
+
+  return offset.replace(GMT, `${GMT} `);
+};
+
+const getTimezoneTitle = (timeZone: string, date = new Date()): string | undefined => {
+  if (!dateUtilsTs.isValidDate(date)) {
+    return '';
+  }
+
+  const tzNamePart = timeZone.replace(/\//g, ' - ').replace(/_/g, ' ');
+  const offset = getStringOffset(timeZone, date);
+  if (offset === undefined) {
+    return undefined;
+  }
+
+  const offsetNamePart = getOffsetNamePart(offset);
+  return `(${offsetNamePart}) ${tzNamePart}`;
+};
+
+// eslint-disable-next-line @typescript-eslint/naming-convention
+const _getDaylightOffsetByTimezone = (startDate: Date, endDate: Date, timeZone: string): number => {
+  const startDayOffset = calculateTimezoneByValue(timeZone, startDate);
+  const endDayOffset = calculateTimezoneByValue(timeZone, endDate);
+  if (startDayOffset === undefined || endDayOffset === undefined) {
+    return 0;
+  }
+
+  return startDayOffset - endDayOffset;
+};
+
+const getCorrectedDateByDaylightOffsets = (
+  convertedOriginalStartDate: Date,
+  convertedDate: Date,
+  date: Date,
+  timeZone: string,
+  startDateTimezone: string,
+): Date => {
+  const daylightOffsetByCommonTimezone = _getDaylightOffsetByTimezone(
+    convertedOriginalStartDate,
+    convertedDate,
+    timeZone,
+  );
+  const daylightOffsetByAppointmentTimezone = _getDaylightOffsetByTimezone(
+    convertedOriginalStartDate,
+    convertedDate,
+    startDateTimezone,
+  );
+  const diff = daylightOffsetByCommonTimezone - daylightOffsetByAppointmentTimezone;
+
+  return new Date(date.getTime() - diff * toMs('hour'));
+};
+
+const correctRecurrenceExceptionByTimezone = (
+  exception: Date,
+  exceptionByStartDate: Date,
+): Date => {
+  const timezoneOffset = (exception.getTimezoneOffset() - exceptionByStartDate.getTimezoneOffset())
+  / MINUTES_IN_HOUR;
+
+  return new Date(exception.getTime() + timezoneOffset * toMs('hour'));
+};
+
+const isTimezoneChangeInDate = (date: Date | number): boolean => {
+  const startDayDate = new Date(new Date(date).setHours(0, 0, 0, 0));
+  const endDayDate = new Date(new Date(date).setHours(23, 59, 59, 0));
+  return (startDayDate.getTimezoneOffset() - endDayDate.getTimezoneOffset()) !== 0;
+};
+
+const getDateWithoutTimezoneChange = (date: Date | number): Date => {
+  const clonedDate = new Date(date);
+  if (isTimezoneChangeInDate(clonedDate)) {
+    const result = new Date(clonedDate);
+    return new Date(result.setDate(result.getDate() + 1));
+  }
+  return clonedDate;
+};
+
+const isSameAppointmentDates = (startDate: Date, endDate: Date): boolean => {
+  // NOTE: subtract 1 millisecond to avoid 00.00 time. Method should return 'true' for
+  // "2020:10:10 22:00:00" and "2020:10:11 00:00:00", for example.
+  const adjustedEndDate = new Date(endDate.getTime() - 1);
+
+  return dateUtils.sameDate(startDate, adjustedEndDate);
+};
+
+const getClientTimezoneOffset = (date = new Date()): number => date.getTimezoneOffset()
+* MS_IN_MINUTE;
+
+const getDiffBetweenClientTimezoneOffsets = (
+  firstDate = new Date(),
+  secondDate = new Date(),
+): number => getClientTimezoneOffset(firstDate) - getClientTimezoneOffset(secondDate);
+
+const addOffsetsWithoutDST = (date: Date, ...offsets: number[]): Date => {
+  const newDate = dateUtilsTs.addOffsets(date, ...offsets);
+  const daylightShift = getDaylightOffsetInMs(date, newDate);
+
+  if (!daylightShift) {
+    return newDate;
+  }
+
+  const correctLocalDate = dateUtilsTs.addOffsets(newDate, -daylightShift);
+  const daylightSecondShift = getDaylightOffsetInMs(newDate, correctLocalDate);
+
+  return !daylightSecondShift
+    ? correctLocalDate
+    : newDate;
+};
+
+const getTimeZones = (
+  date = new Date(),
+  timeZones = timeZoneList.value,
+): TimezoneData[] => timeZones.map((timezoneId) => ({
+  id: timezoneId,
+  title: getTimezoneTitle(timezoneId, date),
+  offset: calculateTimezoneByValue(timezoneId, date),
+}));
+
+const GET_TIMEZONES_BATCH_SIZE = 10;
+const cacheTimeZones = async (): Promise<TimezoneLabel[]> => globalCache.timezones.memo(
+  'timeZonesCachePromise',
+  () => macroTaskArray
+    .map(
+      timeZoneList.value,
+      (timezoneId) => ({
+        id: timezoneId,
+        title: getTimezoneTitle(timezoneId, new Date()),
+      }),
+      GET_TIMEZONES_BATCH_SIZE,
+    )
+    .then((data) => globalCache.timezones.memo('timeZonesCache', () => data)),
+);
+
+const getTimeZonesCache = (): TimezoneLabel[] => globalCache.timezones.get('timeZonesCache') ?? [];
+
+const isLocalTimeMidnightDST = (date: Date): boolean => {
+  const startDayDate = new Date(date.getFullYear(), date.getMonth(), date.getDate());
+
+  return startDayDate.getHours() === 1;
+};
+
+const utils = {
+  getDaylightOffset,
+  getDaylightOffsetInMs,
+  getTimezoneOffsetChangeInMinutes,
+  getTimezoneOffsetChangeInMs,
+  calculateTimezoneByValue,
+  getCorrectedDateByDaylightOffsets,
+  isSameAppointmentDates,
+  correctRecurrenceExceptionByTimezone,
+  getClientTimezoneOffset,
+  getDiffBetweenClientTimezoneOffsets,
+
+  createUTCDateWithLocalOffset,
+  createDateFromUTCWithLocalOffset,
+
+  isTimezoneChangeInDate,
+  getDateWithoutTimezoneChange,
+  getMachineTimezoneName,
+  isEqualLocalTimeZone,
+
+  addOffsetsWithoutDST,
+
+  getTimeZones,
+  getTimeZonesCache,
+  cacheTimeZones,
+
+  isLocalTimeMidnightDST,
+};
+
+export default utils;
diff --git a/packages/devextreme/js/__internal/scheduler/view_model/common/get_compare_options.ts b/packages/devextreme/js/__internal/scheduler/view_model/common/get_compare_options.ts
index 203db8f64802..6fbd9b9b0391 100644
--- a/packages/devextreme/js/__internal/scheduler/view_model/common/get_compare_options.ts
+++ b/packages/devextreme/js/__internal/scheduler/view_model/common/get_compare_options.ts
@@ -1,5 +1,5 @@
 import type Scheduler from '../../m_scheduler';
-import timeZoneUtils from '../../m_utils_time_zone';
+import timeZoneUtils from '../../utils_time_zone';
 import type { CompareOptions } from '../types';
 
 export const getCompareOptions = (
@@ -10,8 +10,8 @@ export const getCompareOptions = (
   const compareOptions = {
     startDayHour: schedulerStore.getViewOption('startDayHour'),
     endDayHour: schedulerStore.getViewOption('endDayHour'),
-    min: timeZoneUtils.createUTCDateWithLocalOffset(dateRange[0]).getTime(),
-    max: timeZoneUtils.createUTCDateWithLocalOffset(dateRange[1]).getTime(),
+    min: (timeZoneUtils.createUTCDateWithLocalOffset(dateRange[0]) as Date).getTime(),
+    max: (timeZoneUtils.createUTCDateWithLocalOffset(dateRange[1]) as Date).getTime(),
     skippedDays: schedulerStore.getViewOption('hiddenWeekDays') as number[],
   };
 
diff --git a/packages/devextreme/js/__internal/scheduler/view_model/generate_view_model/steps/virtual_screen_filter.ts b/packages/devextreme/js/__internal/scheduler/view_model/generate_view_model/steps/virtual_screen_filter.ts
index 1afd763e3c00..9f440bd72b38 100644
--- a/packages/devextreme/js/__internal/scheduler/view_model/generate_view_model/steps/virtual_screen_filter.ts
+++ b/packages/devextreme/js/__internal/scheduler/view_model/generate_view_model/steps/virtual_screen_filter.ts
@@ -1,4 +1,4 @@
-import timeZoneUtils from '../../../m_utils_time_zone';
+import timeZoneUtils from '../../../utils_time_zone';
 import type ViewDataProvider from '../../../workspaces/view_model/m_view_data_provider';
 import { isAppointmentMatchedIntervals } from '../../common/is_appointment_matched_intervals';
 import type { ListEntity } from '../../types';
@@ -16,8 +16,8 @@ export const filterByVirtualScreen = <T extends ListEntity>(
   const groupIntervalsMap = new Map<number, { min: number; max: number }>();
   groupsInfo.forEach((group) => {
     groupIntervalsMap.set(group.groupIndex, {
-      min: timeZoneUtils.createUTCDateWithLocalOffset(group.startDate).getTime(),
-      max: timeZoneUtils.createUTCDateWithLocalOffset(group.endDate).getTime(),
+      min: (timeZoneUtils.createUTCDateWithLocalOffset(group.startDate) as Date).getTime(),
+      max: (timeZoneUtils.createUTCDateWithLocalOffset(group.endDate) as Date).getTime(),
     });
   });
 

From 7050013eaeb13e202b5d64eff6d856b8c5f7c3d7 Mon Sep 17 00:00:00 2001
From: Maksim Zakharov <251575087+bit-byte0@users.noreply.github.com>
Date: Thu, 4 Jun 2026 17:04:17 +0400
Subject: [PATCH 3/9] fix(scheduler): use unknown params in utils to accept
 class instances

---
 .../js/__internal/scheduler/utils.ts          | 34 +++++++------------
 1 file changed, 13 insertions(+), 21 deletions(-)

diff --git a/packages/devextreme/js/__internal/scheduler/utils.ts b/packages/devextreme/js/__internal/scheduler/utils.ts
index 3fd18943717e..83953f5343e5 100644
--- a/packages/devextreme/js/__internal/scheduler/utils.ts
+++ b/packages/devextreme/js/__internal/scheduler/utils.ts
@@ -6,27 +6,17 @@ import { getOuterHeight, setHeight, setWidth } from '@js/core/utils/size';
 import { APPOINTMENT_SETTINGS_KEY } from './constants';
 import type { AppointmentViewModelPlain } from './view_model/types';
 
-interface HeaderWithElement {
-  [key: string]: unknown;
-}
-
-interface RenovationWidget {
-  [key: string]: unknown;
-}
-
 export const utils = {
   dataAccessors: {
     getAppointmentSettings: (
-      element: Element,
-    ): AppointmentViewModelPlain | undefined => $(element)
+      element: unknown,
+    ): AppointmentViewModelPlain | undefined => $(element as Element)
       .data(APPOINTMENT_SETTINGS_KEY) as unknown as AppointmentViewModelPlain | undefined,
   },
   DOM: {
-    getHeaderHeight: (
-      header: HeaderWithElement | null | undefined,
-    ): number => {
-      const $element = header?._$element as
-        dxElementWrapper | undefined;
+    getHeaderHeight: (header: unknown): number => {
+      const $element = (header as Record<string, unknown>)
+        ?._$element as dxElementWrapper | undefined;
       return $element
         ? parseInt(getOuterHeight($element), 10)
         : 0;
@@ -34,28 +24,30 @@ export const utils = {
   },
   renovation: {
     renderComponent: (
-      widget: RenovationWidget,
+      widget: unknown,
       parentElement: dxElementWrapper,
       componentClass: unknown,
       componentName: string,
       viewModel: Record<string, unknown>,
     ): void => {
-      let component = widget[componentName] as
+      const w = widget as Record<string, unknown>;
+      let component = w[componentName] as
         Record<string, Function> | undefined;
       if (!component) {
         const container = getPublicElement(parentElement);
-        const createComponent = widget._createComponent as
-          Function;
+        const createComponent = w._createComponent as Function;
         component = createComponent(
           container,
           componentClass,
           viewModel,
         ) as Record<string, Function>;
-        widget[componentName] = component;
+        w[componentName] = component;
       } else {
         const $element = component.$element() as
           dxElementWrapper;
-        const elementStyle = ($element.get(0) as HTMLElement).style;
+        const elementStyle = (
+          $element.get(0) as HTMLElement
+        ).style;
         const { height } = elementStyle;
         const { width } = elementStyle;
 

From a032aba21b01a140312624e505c172275d5c58ea Mon Sep 17 00:00:00 2001
From: Maksim Zakharov <251575087+bit-byte0@users.noreply.github.com>
Date: Thu, 4 Jun 2026 17:11:56 +0400
Subject: [PATCH 4/9] fix(scheduler): resolve build errors and review feedback

---
 .../js/__internal/scheduler/r1/utils/agenda.pacific.test.ts   | 4 ++--
 .../js/__internal/scheduler/r1/utils/agenda.santiago.test.ts  | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.pacific.test.ts b/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.pacific.test.ts
index 221ec0c810cf..d3b2f56c1d6b 100644
--- a/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.pacific.test.ts
+++ b/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.pacific.test.ts
@@ -10,8 +10,8 @@ import { calculateRows } from './agenda';
 const createDate = (year: number, month: number, day: number, hours: number) => {
   const date = timeZoneUtils.createUTCDateWithLocalOffset(
     new Date(year, month, day, hours),
-  );
-  return date ? date.getTime() : 0;
+  ) as Date;
+  return date.getTime();
 };
 
 describe('calculateRows', () => {
diff --git a/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.santiago.test.ts b/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.santiago.test.ts
index 5c9a66868afb..33eacd3b0242 100644
--- a/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.santiago.test.ts
+++ b/packages/devextreme/js/__internal/scheduler/r1/utils/agenda.santiago.test.ts
@@ -10,8 +10,8 @@ import { calculateRows } from './agenda';
 const createDate = (year: number, month: number, day: number, hours: number) => {
   const date = timeZoneUtils.createUTCDateWithLocalOffset(
     new Date(year, month, day, hours),
-  );
-  return date ? date.getTime() : 0;
+  ) as Date;
+  return date.getTime();
 };
 
 describe('calculateRows', () => {

From 77c88503e4656bf58c979253ec3f5ecf920e693d Mon Sep 17 00:00:00 2001
From: Maksim Zakharov <251575087+bit-byte0@users.noreply.github.com>
Date: Thu, 4 Jun 2026 17:25:44 +0400
Subject: [PATCH 5/9] fix(scheduler): update missed import in public API
 re-export

---
 .../devextreme/js/common/core/environment/time_zone_utils.js    | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/devextreme/js/common/core/environment/time_zone_utils.js b/packages/devextreme/js/common/core/environment/time_zone_utils.js
index 4bbab0e11a5e..d27b4e7dc42a 100644
--- a/packages/devextreme/js/common/core/environment/time_zone_utils.js
+++ b/packages/devextreme/js/common/core/environment/time_zone_utils.js
@@ -1,3 +1,3 @@
-import timeZoneUtils from '../../../__internal/scheduler/m_utils_time_zone';
+import timeZoneUtils from '../../../__internal/scheduler/utils_time_zone';
 
 export const getTimeZones = timeZoneUtils.getTimeZones;

From ffc51b289236348423efba74ac26b053404ab01d Mon Sep 17 00:00:00 2001
From: Maksim Zakharov <251575087+bit-byte0@users.noreply.github.com>
Date: Thu, 4 Jun 2026 19:07:21 +0400
Subject: [PATCH 6/9] fix(scheduler): preserve original logic in utils
 renderComponent

---
 .../js/__internal/scheduler/utils.ts          | 29 +++++++------------
 1 file changed, 10 insertions(+), 19 deletions(-)

diff --git a/packages/devextreme/js/__internal/scheduler/utils.ts b/packages/devextreme/js/__internal/scheduler/utils.ts
index 83953f5343e5..f2536284d39c 100644
--- a/packages/devextreme/js/__internal/scheduler/utils.ts
+++ b/packages/devextreme/js/__internal/scheduler/utils.ts
@@ -15,10 +15,9 @@ export const utils = {
   },
   DOM: {
     getHeaderHeight: (header: unknown): number => {
-      const $element = (header as Record<string, unknown>)
-        ?._$element as dxElementWrapper | undefined;
-      return $element
-        ? parseInt(getOuterHeight($element), 10)
+      const h = header as Record<string, unknown> | null | undefined;
+      return h?._$element
+        ? parseInt(getOuterHeight(h._$element as dxElementWrapper), 10)
         : 0;
     },
   },
@@ -30,28 +29,20 @@ export const utils = {
       componentName: string,
       viewModel: Record<string, unknown>,
     ): void => {
-      const w = widget as Record<string, unknown>;
-      let component = w[componentName] as
-        Record<string, Function> | undefined;
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      const w = widget as any;
+      let component = w[componentName];
       if (!component) {
         const container = getPublicElement(parentElement);
-        const createComponent = w._createComponent as Function;
-        component = createComponent(
-          container,
-          componentClass,
-          viewModel,
-        ) as Record<string, Function>;
+        component = w._createComponent(container, componentClass, viewModel);
         w[componentName] = component;
       } else {
-        const $element = component.$element() as
-          dxElementWrapper;
-        const elementStyle = (
-          $element.get(0) as HTMLElement
-        ).style;
+        const $element = component.$element() as dxElementWrapper;
+        const elementStyle = ($element.get(0) as HTMLElement).style;
         const { height } = elementStyle;
         const { width } = elementStyle;
 
-        (component.option)(viewModel);
+        component.option(viewModel);
 
         if (height) {
           setHeight($element, height);

From c4a3fce220c7f5dafcfa575382cd3a00df66a730 Mon Sep 17 00:00:00 2001
From: Maksim Zakharov <251575087+bit-byte0@users.noreply.github.com>
Date: Thu, 4 Jun 2026 19:46:47 +0400
Subject: [PATCH 7/9] fix(scheduler): type getAppointmentSettings param as
 dxElementWrapper

---
 packages/devextreme/js/__internal/scheduler/utils.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/devextreme/js/__internal/scheduler/utils.ts b/packages/devextreme/js/__internal/scheduler/utils.ts
index f2536284d39c..8c9e22196cd2 100644
--- a/packages/devextreme/js/__internal/scheduler/utils.ts
+++ b/packages/devextreme/js/__internal/scheduler/utils.ts
@@ -9,8 +9,8 @@ import type { AppointmentViewModelPlain } from './view_model/types';
 export const utils = {
   dataAccessors: {
     getAppointmentSettings: (
-      element: unknown,
-    ): AppointmentViewModelPlain | undefined => $(element as Element)
+      element: dxElementWrapper,
+    ): AppointmentViewModelPlain | undefined => $(element)
       .data(APPOINTMENT_SETTINGS_KEY) as unknown as AppointmentViewModelPlain | undefined,
   },
   DOM: {

From fa080ddb847be89872600f7e7a13c6380714257f Mon Sep 17 00:00:00 2001
From: Maksim Zakharov <251575087+bit-byte0@users.noreply.github.com>
Date: Fri, 5 Jun 2026 18:33:38 +0400
Subject: [PATCH 8/9] fix(scheduler): sort imports in workspace files

---
 .../js/__internal/scheduler/workspaces/m_work_space.ts          | 2 +-
 .../devextreme/js/__internal/scheduler/workspaces/timeline.ts   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/devextreme/js/__internal/scheduler/workspaces/m_work_space.ts b/packages/devextreme/js/__internal/scheduler/workspaces/m_work_space.ts
index 59438594a231..90884d0a8a8e 100644
--- a/packages/devextreme/js/__internal/scheduler/workspaces/m_work_space.ts
+++ b/packages/devextreme/js/__internal/scheduler/workspaces/m_work_space.ts
@@ -73,9 +73,9 @@ import AppointmentDragBehavior from '../m_appointment_drag_behavior';
 import { CompactAppointmentsHelper } from '../m_compact_appointments_helper';
 import type { SubscribeKey, SubscribeMethods } from '../m_subscribes';
 import tableCreatorModule, { type GroupRows } from '../m_table_creator';
-import { utils } from '../utils';
 import VerticalShader from '../shaders/current_time_shader_vertical';
 import type { ViewCellData } from '../types';
+import { utils } from '../utils';
 import type { ResourceLoader } from '../utils/loader/resource_loader';
 import {
   getAppointmentGroupIndex,
diff --git a/packages/devextreme/js/__internal/scheduler/workspaces/timeline.ts b/packages/devextreme/js/__internal/scheduler/workspaces/timeline.ts
index 4aa823777848..a847ee8da4a0 100644
--- a/packages/devextreme/js/__internal/scheduler/workspaces/timeline.ts
+++ b/packages/devextreme/js/__internal/scheduler/workspaces/timeline.ts
@@ -17,10 +17,10 @@ import {
   GROUP_ROW_CLASS,
 } from '../classes';
 import tableCreatorModule, { type GroupRows } from '../m_table_creator';
-import timezoneUtils from '../utils_time_zone';
 import HorizontalShader from '../shaders/current_time_shader_horizontal';
 import type { ResourceLoader } from '../utils/loader/resource_loader';
 import { getFirstVisibleDate } from '../utils/skipped_days';
+import timezoneUtils from '../utils_time_zone';
 import type { WorkspaceOptionsInternal } from './m_work_space';
 import type { ViewDataProviderOptions } from './view_model/m_types';
 import SchedulerWorkSpace from './work_space_indicator';

From 79775cbd2755e5a22749314cc4f993996d124321 Mon Sep 17 00:00:00 2001
From: Maksim Zakharov <251575087+bit-byte0@users.noreply.github.com>
Date: Fri, 5 Jun 2026 19:37:32 +0400
Subject: [PATCH 9/9] fix(scheduler): sort imports in appointment_collection
 and base

---
 .../scheduler/appointments/m_appointment_collection.ts          | 2 +-
 packages/devextreme/js/__internal/scheduler/r1/utils/base.ts    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/devextreme/js/__internal/scheduler/appointments/m_appointment_collection.ts b/packages/devextreme/js/__internal/scheduler/appointments/m_appointment_collection.ts
index a27cab8d43dd..26add8462075 100644
--- a/packages/devextreme/js/__internal/scheduler/appointments/m_appointment_collection.ts
+++ b/packages/devextreme/js/__internal/scheduler/appointments/m_appointment_collection.ts
@@ -27,7 +27,6 @@ import {
   APPOINTMENT_ITEM_CLASS,
 } from '../classes';
 import { APPOINTMENT_SETTINGS_KEY } from '../constants';
-import timeZoneUtils from '../utils_time_zone';
 import type { CompactAppointmentOptions } from '../types';
 import { AppointmentAdapter } from '../utils/appointment_adapter/appointment_adapter';
 import type { AppointmentDataAccessor } from '../utils/data_accessor/appointment_data_accessor';
@@ -38,6 +37,7 @@ import {
 import { getAppointmentGroupValues } from '../utils/resource_manager/appointment_groups_utils';
 import { getGroupTexts } from '../utils/resource_manager/group_utils';
 import type { ResourceManager } from '../utils/resource_manager/resource_manager';
+import timeZoneUtils from '../utils_time_zone';
 import type {
   AppointmentAgendaViewModel,
   AppointmentCollectorViewModel,
diff --git a/packages/devextreme/js/__internal/scheduler/r1/utils/base.ts b/packages/devextreme/js/__internal/scheduler/r1/utils/base.ts
index bcb7457a933d..6282960638dc 100644
--- a/packages/devextreme/js/__internal/scheduler/r1/utils/base.ts
+++ b/packages/devextreme/js/__internal/scheduler/r1/utils/base.ts
@@ -7,7 +7,6 @@ import { VERTICAL_GROUP_COUNT_CLASSES } from '../../classes';
 import {
   HORIZONTAL_GROUP_ORIENTATION, VERTICAL_GROUP_ORIENTATION,
 } from '../../constants';
-import timeZoneUtils from '../../utils_time_zone';
 import type {
   AllDayPanelModeType,
   AppointmentGeometry,
@@ -24,6 +23,7 @@ import type {
 import type { ResourceLoader } from '../../utils/loader/resource_loader';
 import type { ResourceId } from '../../utils/loader/types';
 import { VIEWS } from '../../utils/options/constants_view';
+import timeZoneUtils from '../../utils_time_zone';
 
 const toMs = dateUtils.dateToMilliseconds;
 const DAY_HOURS = 24;