Fix recurrence part position and size after daylights saving change (T804886, first step)

js/ui/scheduler/ui.scheduler.appointments.js

@@ -807,6 +807,7 @@ const SchedulerAppointments = CollectionWidget.inherit({
     },
 
     _processRecurrenceAppointment: function(appointment, index, skipLongAppointments) {
+        // NOTE: this method is actual only for agenda
         const recurrenceRule = this.invoke('getField', 'recurrenceRule', appointment);
         const result = {
             parts: [],

js/ui/scheduler/ui.scheduler.js

@@ -1060,6 +1060,35 @@ const Scheduler = Widget.inherit({
         return this._calculateTimezoneByValue(this.option('timeZone'), date);
     },
 
+    _getDaylightOffsetByCustomTimezone: function(startDate, endDate) {
+        return this._getTimezoneOffsetByOption(startDate) - this._getTimezoneOffsetByOption(endDate);
+    },
+
+    _getDaylightOffsetByAppointmentTimezone: function(startDate, endDate, appointmentTimezone) {
+        return this._calculateTimezoneByValue(appointmentTimezone, startDate) - this._calculateTimezoneByValue(appointmentTimezone, endDate);
+    },
+
+    _getCorrectedDateByDaylightOffsets: function(originalStartDate, date, startDateTimezone) {
+        const daylightOffsetByOption = this._getDaylightOffsetByCustomTimezone(originalStartDate, date);
+        const daylightOffsetByAppointment = this._getDaylightOffsetByAppointmentTimezone(originalStartDate, date, startDateTimezone);
+        const diff = daylightOffsetByOption - daylightOffsetByAppointment;
+
+        return new Date(date.getTime() - diff * toMs('hour'));
+    },
+
+    getCorrectedDatesByDaylightOffsets: function(originalStartDate, dates, appointmentData) {
+        const startDateTimeZone = this.fire('getField', 'startDateTimeZone', appointmentData);
+        const needCheckTimezoneOffset = typeUtils.isDefined(startDateTimeZone) && typeUtils.isDefined(this._getTimezoneOffsetByOption(originalStartDate));
+
+        if(needCheckTimezoneOffset) {
+            dates = dates.map((date) => {
+                return this._getCorrectedDateByDaylightOffsets(originalStartDate, date, startDateTimeZone);
+            });
+        }
+
+        return dates;
+    },
+
     _calculateTimezoneByValue: function(timezone, date) {
         let result = timezone;
 

js/ui/scheduler/ui.scheduler.subscribes.js

@@ -61,7 +61,9 @@ const subscribes = {
             dates.push(startDate);
             initialDates = dates;
         } else {
+            dates = this.getCorrectedDatesByDaylightOffsets(originalStartDate, dates, appointmentData);
             initialDates = dates;
+
             dates = dates.map((date) => {
                 return dateUtils.roundDateByStartDayHour(date, this._getCurrentViewOption('startDayHour'));
             });