diff --git a/application/Espo/Entities/Preferences.php b/application/Espo/Entities/Preferences.php
index 61d0388dbc..68979d2eb4 100644
--- a/application/Espo/Entities/Preferences.php
+++ b/application/Espo/Entities/Preferences.php
@@ -42,4 +42,9 @@ class Preferences extends \Espo\Core\ORM\Entity
     {
         return null;
     }
+
+    public function getTimeZone(): ?string
+    {
+        return $this->get('timeZone');
+    }
 }
diff --git a/application/Espo/Modules/Crm/Tools/Calendar/Service.php b/application/Espo/Modules/Crm/Tools/Calendar/Service.php
index f40448d388..18f8ae3a91 100644
--- a/application/Espo/Modules/Crm/Tools/Calendar/Service.php
+++ b/application/Espo/Modules/Crm/Tools/Calendar/Service.php
@@ -29,6 +29,7 @@
 
 namespace Espo\Modules\Crm\Tools\Calendar;
 
+use DateTimeZone;
 use Espo\Core\Acl;
 use Espo\Core\Acl\Table;
 use Espo\Core\Exceptions\BadRequest;
@@ -39,6 +40,7 @@ use Espo\Core\Field\DateTime as DateTimeField;
 use Espo\Core\Select\SelectBuilderFactory;
 use Espo\Core\Utils\Config;
 use Espo\Core\Utils\Metadata;
+use Espo\Entities\Preferences;
 use Espo\Entities\Team;
 use Espo\Entities\User;
 use Espo\Modules\Crm\Entities\Call;
@@ -891,18 +893,21 @@ class Service
         $from = $fetchParams->getFrom();
         $to = $fetchParams->getTo();
 
+        $timezone = !$fetchParams->isAgenda() ?
+            $this->getCurrentUserTimezone() : null;
+
         $extractor = new Extractor();
 
         $itemList = $fetchParams->workingTimeRangesInverted() ?
             (
             $fetchParams->isAgenda() ?
                 $extractor->extractInversion($calendar, $from, $to) :
-                $extractor->extractAllDayInversion($calendar, $from, $to)
+                $extractor->extractAllDayInversion($calendar, $from, $to, $timezone)
             ) :
             (
             $fetchParams->isAgenda() ?
                 $extractor->extract($calendar, $from, $to) :
-                $extractor->extractAllDay($calendar, $from, $to)
+                $extractor->extractAllDay($calendar, $from, $to, $timezone)
             );
 
         $list = [];
@@ -1015,4 +1020,29 @@ class Service
 
         return $result;
     }
+
+    private function getCurrentUserTimezone(): DateTimeZone
+    {
+        try {
+            return new DateTimeZone($this->getCurrentUserTimezoneString());
+        } catch (Exception $e) {
+            throw new RuntimeException($e->getMessage(), 0, $e);
+        }
+    }
+
+    /**
+     * @todo Move to a separate class.
+     */
+    private function getCurrentUserTimezoneString(): string
+    {
+        $preferences = $this->entityManager
+            ->getRepositoryByClass(Preferences::class)
+            ->getById($this->user->getId());
+
+        if ($preferences && $preferences->getTimeZone()) {
+            return $preferences->getTimeZone();
+        }
+
+        return $this->config->get('timeZone') ?? 'UTC';
+    }
 }
diff --git a/application/Espo/Tools/WorkingTime/Extractor.php b/application/Espo/Tools/WorkingTime/Extractor.php
index befe4b00dd..aa1db5a72f 100644
--- a/application/Espo/Tools/WorkingTime/Extractor.php
+++ b/application/Espo/Tools/WorkingTime/Extractor.php
@@ -29,6 +29,7 @@
 
 namespace Espo\Tools\WorkingTime;
 
+use DateTimeZone;
 use Espo\Tools\WorkingTime\Calendar\WorkingWeekday;
 use Espo\Tools\WorkingTime\Calendar\WorkingDate;
 use Espo\Tools\WorkingTime\Calendar\HavingRanges;
@@ -137,10 +138,16 @@ class Extractor
     /**
      * @return array{DateTime,DateTime}[]
      */
-    public function extractAllDay(Calendar $calendar, DateTime $from, DateTime $to): array
-    {
+    public function extractAllDay(Calendar $calendar,
+        DateTime $from,
+        DateTime $to,
+        ?DateTimeZone $timezone = null
+    ): array {
+
+        $timezone ??= $calendar->getTimezone();
+
         $pointer = $from
-            ->withTimezone($calendar->getTimezone())
+            ->withTimezone($timezone)
             ->withTime(0, 0, 0);
 
         $fromDate = Date::fromDateTime($from->modify('-1 day')->toDateTime());
@@ -152,7 +159,7 @@ class Extractor
 
         $list = [];
 
-        $end = $to->withTimezone($calendar->getTimezone())->withTime(23, 59, 59);
+        $end = $to->withTimezone($timezone)->withTime(23, 59, 59);
 
         while ($pointer->toTimestamp() < $end->toTimestamp()) {
             $isWorkingDay = $this->isWorkingDay(
@@ -225,9 +232,14 @@ class Extractor
     /**
      * @return array{DateTime,DateTime}[]
      */
-    public function extractAllDayInversion(Calendar $calendar, DateTime $from, DateTime $to): array
-    {
-        $list = $this->extractAllDay($calendar, $from, $to);
+    public function extractAllDayInversion(
+        Calendar $calendar,
+        DateTime $from,
+        DateTime $to,
+        ?DateTimeZone $timezone = null
+    ): array {
+
+        $list = $this->extractAllDay($calendar, $from, $to, $timezone);
 
         if ($list === []) {
             return [[$from, $to]];