Fixed missing offset from daylight savings time

[twirth5]

When the humhub calender is imported into outlook for windows, all entries that are defined after the 27th of march (change from standard time to daylight savings time) are off by +1 hour.

Our quick fix was, to hard code the timezone into the withEvents() method of VCalendar, so that the correct header is added to the exported ics.

[ArchBlood]

@luke-, instead of this approach how about implementing this into the calendar module.

Current

    /**
     * @param CalendarEventIF[] $items
     * @return VCalendar
     */
    public static function withEvents($items, $tz = null)
    {
        $instance = (new static());
        $instance->addTimeZone($tz);

        if(!is_array($items)) {
            $items = [$items];
        }

        foreach ($items as $item)
        {
            if(is_array($item)) {
                $item = new CalendarEventIFWrapper(['options' => $item]);
            }
            $instance->addVEvent($item);
        }


        return  $instance;
    }

After

/**
 * @param CalendarEventIF[] $items
 * @return VCalendar
 */
public static function withEvents($items, $tz = null)
{
    $instance = (new static());
    
    // Retrieve default timezone from Yii::$app->settings
    $defaultTimeZone = Yii::$app->settings->get('defaultTimeZone');

    $instance->addTimeZone($defaultTimeZone);

    if (!is_array($items)) {
        $items = [$items];
    }

    foreach ($items as $item) {
        if (is_array($item)) {
            $item = new CalendarEventIFWrapper(['options' => $item]);
        }

        // Assuming $item has a start time property
        $itemStartTime = $item->getStartTime(); // Get the start time of the event

        // Create a DateTime object with the provided start time
        $startDateTime = new DateTime($itemStartTime);

        // Set the time zone to the default timezone retrieved from Yii::$app->settings
        $startDateTime->setTimezone(new DateTimeZone($defaultTimeZone));

        // Add one hour considering daylight saving time
        $startDateTime->modify('+1 hour');

        // Set the modified start time back to the event
        $item->setStartTime($startDateTime->format('Y-m-d H:i:s'));

        $instance->addVEvent($item);
    }

    return $instance;
}

We could also dig deeper for PHP 8.0 and use something like this;

public static function withEvents(array $items, $tz = null): VCalendar
{
    $instance = new static();

    $defaultTimeZone = Yii::$app->settings->get('defaultTimeZone');

    $instance->addTimeZone($defaultTimeZone);

    foreach ($items as $item) {
        $item = is_array($item) ? new CalendarEventIFWrapper(['options' => $item]) : $item;

        $itemStartTime = $item->getStartTime();

        $startDateTime = new DateTime($itemStartTime);

        $startDateTime->setTimezone(new DateTimeZone($defaultTimeZone))
                      ->modify('+1 hour');

        $item->setStartTime($startDateTime->format('Y-m-d H:i:s'));

        $instance->addVEvent($item);
    }

    return $instance;
}