diff --git a/calendar_ui.js b/calendar_ui.js
index 4d6bb2a..0a04879 100644
--- a/calendar_ui.js
+++ b/calendar_ui.js
@@ -2035,12 +2035,17 @@ function rcube_calendar_ui(settings)
       }
       
       icon = $(icon).attr('class', 'availabilityicon loading');
-      
+
+      var start = event.allDay ? '00:00' : $('#edit-starttime').val();
+      var end = event.allDay ? '23:59' : $('#edit-endtime').val();
+      var start = me.parse_datetime(start, $('#edit-startdate').val());
+      var end   = me.parse_datetime(end, $('#edit-enddate').val());
+
       $.ajax({
         type: 'GET',
         dataType: 'html',
         url: rcmail.url('freebusy-status'),
-        data: { email:email, start:date2servertime(clone_date(event.start, event.allDay?1:0)), end:date2servertime(clone_date(event.end, event.allDay?2:0)), _remote: 1 },
+        data: { email:email, start:date2servertime(start), end:date2servertime(end), _remote: 1 },
         success: function(status){
           var avail = String(status).toLowerCase();
           icon.removeClass('loading').addClass(avail).attr('title', rcmail.gettext('avail' + avail, 'calendar'));
diff --git a/drivers/caldav/SQL/mysql.initial.sql b/drivers/caldav/SQL/mysql.initial.sql
index 92004b2..c41d620 100644
--- a/drivers/caldav/SQL/mysql.initial.sql
+++ b/drivers/caldav/SQL/mysql.initial.sql
@@ -107,4 +107,4 @@ CREATE TABLE IF NOT EXISTS `caldav_attachments` (
     CONSTRAINT `fk_caldav_attachments_event_id` FOREIGN KEY (`event_id`)
         REFERENCES `caldav_events`(`event_id`) ON DELETE CASCADE ON UPDATE CASCADE
 ) /*!40000 ENGINE=INNODB */ /*!40101 CHARACTER SET utf8 COLLATE utf8_general_ci */;
-REPLACE INTO `system` (`name`, `value`) VALUES ('calendar-caldav-version', '2021082400');
\ No newline at end of file
+REPLACE INTO `system` (`name`, `value`) VALUES ('calendar-caldav-version', '2024112200');
\ No newline at end of file
diff --git a/drivers/caldav/SQL/postgres.initial.sql b/drivers/caldav/SQL/postgres.initial.sql
index 80ee79f..c8515b2 100644
--- a/drivers/caldav/SQL/postgres.initial.sql
+++ b/drivers/caldav/SQL/postgres.initial.sql
@@ -122,4 +122,4 @@ CREATE TABLE IF NOT EXISTS caldav_attachments (
     REFERENCES caldav_events(event_id) ON DELETE CASCADE ON UPDATE CASCADE
     ) /* SQLINES DEMO *** DB */ /* SQLINES DEMO *** ET utf8 COLLATE utf8_general_ci */;
 
-INSERT INTO system (name, value) VALUES ('calendar-caldav-version', '2021082400') ON CONFLICT (name) DO UPDATE SET value = excluded.value;
+INSERT INTO system (name, value) VALUES ('calendar-caldav-version', '2024112200') ON CONFLICT (name) DO UPDATE SET value = excluded.value;
diff --git a/drivers/caldav/SQL/sqlite.initial.sql b/drivers/caldav/SQL/sqlite.initial.sql
index 3c06c1f..68ad8f7 100644
--- a/drivers/caldav/SQL/sqlite.initial.sql
+++ b/drivers/caldav/SQL/sqlite.initial.sql
@@ -93,7 +93,7 @@ CREATE TABLE IF NOT EXISTS `caldav_attachments` (
     FOREIGN KEY (`event_id`)
         REFERENCES `caldav_events`(`event_id`) ON DELETE CASCADE ON UPDATE CASCADE
 );
-REPLACE INTO `system` (`name`, `value`) VALUES ('calendar-caldav-version', '2021082400');
+REPLACE INTO `system` (`name`, `value`) VALUES ('calendar-caldav-version', '2024112200');
 
 CREATE INDEX caldav_user_name_idx ON caldav_calendars(user_id, name);
 CREATE INDEX caldav_uid_idx ON caldav_events(uid);
diff --git a/drivers/caldav/caldav_client.php b/drivers/caldav/caldav_client.php
index 95f6789..7799ab7 100644
--- a/drivers/caldav/caldav_client.php
+++ b/drivers/caldav/caldav_client.php
@@ -400,5 +400,31 @@ public function delete_calendar() {
         return $response["statusCode"] === 204 ||    // 204 (no content, successfully deleted)
             $response["statusCode"] === 200;      // 200 (OK, successfully deleted)
     }
+
+    /**
+     * Fetch freebusy info.
+     *
+     * @return Sabre\VObject\Component\VFreeBusy
+     */
+    public function get_freebusy_info($path, $body) {
+        $headers = ['Content-Type' => 'text/calendar; charset=utf-8'];
+
+        $response = $this->request('POST', $path, $body, $headers);
+        if ($response['statusCode'] !== 200) {
+            rcmail::console('Could not get freebusy info for user. Response: ' . print_r($response, true));
+
+            return false;
+        }
+
+        $schedule_response = $this->xml->expect('{urn:ietf:params:xml:ns:caldav}schedule-response', $response['body'])[0]['value'];
+        $calendar_data = array_values(array_filter(
+            $schedule_response,
+            function ($arr) {
+                return $arr['name'] == '{urn:ietf:params:xml:ns:caldav}calendar-data';
+            }
+        ))[0]['value'];
+
+        return Sabre\VObject\Reader::read($calendar_data)->VFREEBUSY;
+    }
 };
 ?>
diff --git a/drivers/caldav/caldav_driver.php b/drivers/caldav/caldav_driver.php
index 71a2162..4a2f36c 100644
--- a/drivers/caldav/caldav_driver.php
+++ b/drivers/caldav/caldav_driver.php
@@ -36,7 +36,7 @@ class caldav_driver extends calendar_driver
     // features this backend supports
     public $alarms = true;
     public $attendees = true;
-    public $freebusy = false;
+    public $freebusy = true;
     public $attachments = true;
     public $alarm_types = array('DISPLAY');
 
@@ -1784,6 +1784,88 @@ public function replace_category($oldname, $name, $color)
         return $this->rc->db->affected_rows($query);
     }
 
+    public function get_freebusy_list($email, $start, $end) {
+        $result = $this->rc->db->query(
+            'SELECT source_id, caldav_url, caldav_user, caldav_pass
+            FROM ' . $this->db_sources . '
+            WHERE user_id=?',
+            $this->rc->user->ID,
+        );
+
+        $fbtypemap = [
+            'UNKNOWN' => calendar::FREEBUSY_UNKNOWN,
+            'FREE' => calendar::FREEBUSY_FREE,
+            'BUSY' => calendar::FREEBUSY_BUSY,
+            'TENTATIVE' => calendar::FREEBUSY_TENTATIVE,
+            'OUT-OF-OFFICE' => calendar::FREEBUSY_OOF,
+        ];
+        $freebusy_list = [];
+        $success = false;
+        while ($result && ($source = $this->rc->db->fetch_assoc($result))) {
+            $source['caldav_pass'] = $this->_decrypt_pass($source['caldav_pass']);
+            $server_url = self::_encode_url($source['caldav_url']);
+
+            $caldav = new caldav_client($server_url, $source['caldav_user'], $source['caldav_pass']);
+            $response = $caldav->prop_find($server_url, ['{DAV:}current-user-principal'], 0);
+
+            if (
+                $response
+                && array_key_exists('{DAV:}current-user-principal', $response)
+                && count($response['{DAV:}current-user-principal']) > 0
+                && array_key_exists('value', $response['{DAV:}current-user-principal'][0])
+            ) {
+                $response = $caldav->prop_find(
+                    $response['{DAV:}current-user-principal'][0]['value'],
+                    ['{urn:ietf:params:xml:ns:caldav}schedule-outbox-URL'],
+                    0,
+                );
+
+                if (
+                    $response
+                    && array_key_exists('{urn:ietf:params:xml:ns:caldav}schedule-outbox-URL', $response)
+                    && count($response['{urn:ietf:params:xml:ns:caldav}schedule-outbox-URL']) > 0
+                    && array_key_exists('value', $response['{urn:ietf:params:xml:ns:caldav}schedule-outbox-URL'][0])
+                ) {
+                    $vcalendar = new Sabre\VObject\Component\VCalendar([
+                        'METHOD' => 'REQUEST',
+                        'VFREEBUSY' => [
+                            'ORGANIZER' => 'mailto:' . $this->rc->get_user_name(),
+                            'ATTENDEE' => $email,
+                            'DTSTART' => DateTime::createFromFormat('U', $start),
+                            'DTEND' => DateTime::createFromFormat('U', $end),
+                        ]
+                    ]);
+                    $freebusy_info = $caldav->get_freebusy_info(
+                        $response['{urn:ietf:params:xml:ns:caldav}schedule-outbox-URL'][0]['value'],
+                        $vcalendar->serialize()
+                    );
+
+                    if ($freebusy_info) {
+                        $success = true;
+                        if (isset($freebusy_info->FREEBUSY)) {
+                            foreach ($freebusy_info->FREEBUSY as $freebusy) {
+                                $fbType = isset($freebusy['FBTYPE']) ? (string) $freebusy['FBTYPE'] : 'BUSY';
+                                [$startTime, $endTime] = explode('/', $freebusy->getValue());
+
+                                $freebusy_list[] = [
+                                    strtotime($startTime),
+                                    strtotime($endTime),
+                                    $fbtypemap[strtoupper($fbType)] ?? 0,
+                                ];
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        if ($success) {
+            return $freebusy_list;
+        } else {
+            return false;
+        }
+    }
+
     /**
      * Helper method to serialize the list of alarms into a string
      */