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Incorrect Timezone Handling in CalDAV Synchronization Causes Time Shifts #1626

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Incorrect Timezone Handling in CalDAV Synchronization Causes Time Shifts #1626

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90 changes: 54 additions & 36 deletions application/libraries/Caldav_sync.php
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Original file line number Diff line number Diff line change
Expand Up @@ -466,45 +466,63 @@ private function get_unavailability_ics_file(array $unavailability, array $provi
*
* @throws DateMalformedStringException
*/
private function convert_caldav_event_to_array_event(VEvent $vevent, DateTimeZone $timezone_object): array
private function convert_caldav_event_to_array_event(VEvent $vevent, DateTimeZone $default_timezone): array
{
$utc_timezone_object = new DateTimeZone('UTC'); // Convert from UTC to local provider timezone

$start_date_time_object = new DateTime((string) $vevent->DTSTART, $utc_timezone_object);
$start_date_time_object->setTimezone($timezone_object);

$end_date_time_object = new DateTime((string) $vevent->DTEND, $utc_timezone_object);
$end_date_time_object->setTimezone($timezone_object);

// Check if the event is recurring

$is_recurring_event =
isset($vevent->RRULE) ||
isset($vevent->RDATE) ||
isset($vevent->{'RECURRENCE-ID'}) ||
isset($vevent->EXDATE);

// Generate ID based on recurrence status

$event_id = (string) $vevent->UID;

if ($is_recurring_event) {
$event_id .= '-RECURRENCE-' . random_string();
try {
// Extract the raw DTSTART and DTEND values
$raw_start = (string)$vevent->DTSTART;
$raw_end = (string)$vevent->DTEND;

// Handle timezone extraction
$start_date_time_object = $this->extract_datetime_with_timezone($raw_start, $default_timezone);
$end_date_time_object = $this->extract_datetime_with_timezone($raw_end, $default_timezone);

// Generate event ID (handle recurring events)
$is_recurring_event = isset($vevent->RRULE) || isset($vevent->RDATE) || isset($vevent->{'RECURRENCE-ID'}) || isset($vevent->EXDATE);
$event_id = (string)$vevent->UID;
if ($is_recurring_event) {
$event_id .= '-RECURRENCE-' . bin2hex(random_bytes(8));
}

// Return the event data
return [
'id' => $event_id,
'summary' => (string)$vevent->SUMMARY ?? '',
'start_datetime' => $start_date_time_object->format('Y-m-d H:i:s'),
'end_datetime' => $end_date_time_object->format('Y-m-d H:i:s'),
'description' => (string)$vevent->DESCRIPTION ?? '',
'status' => (string)$vevent->STATUS ?? 'CONFIRMED',
'location' => (string)$vevent->LOCATION ?? '',
];
} catch (Exception $e) {
error_log('Error processing CalDAV event: ' . $e->getMessage());
throw $e;
}
}

private function extract_datetime_with_timezone(string $date_time_string, DateTimeZone $default_timezone): DateTime
{
try {
if (strpos($date_time_string, 'TZID=') !== false) {
// Extract the TZID and use it
preg_match('/TZID=([^:]+):/', $date_time_string, $matches);
$timezone_name = $matches[1];
$date_time_string = preg_replace('/TZID=[^:]+:/', '', $date_time_string);
$date_time_object = new DateTime($date_time_string, new DateTimeZone($timezone_name));
} elseif (substr($date_time_string, -1) === 'Z') {
// Handle UTC timestamps
$date_time_object = new DateTime($date_time_string, new DateTimeZone('UTC'));
} else {
// Default to the provided timezone
$date_time_object = new DateTime($date_time_string, $default_timezone);
}

return $date_time_object;
} catch (Exception $e) {
error_log('Error extracting DateTime with timezone: ' . $e->getMessage());
throw $e;
}

// Return the converted event

return [
'id' => $event_id,
'summary' => (string) $vevent->SUMMARY,
'start_datetime' => $start_date_time_object->format('Y-m-d H:i:s'),
'end_datetime' => $end_date_time_object->format('Y-m-d H:i:s'),
'description' => (string) $vevent->DESCRIPTION,
'status' => (string) $vevent->STATUS,
'location' => (string) $vevent->LOCATION,
];
}

/**
* @throws GuzzleException
* @throws Exception
Expand Down