--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/plugins/libcalendaring/lib/Sabre/VObject/TimeZoneUtil.php	Sat Jan 13 08:57:56 2018 -0500
@@ -0,0 +1,482 @@
+<?php
+
+namespace Sabre\VObject;
+
+/**
+ * Time zone name translation
+ *
+ * This file translates well-known time zone names into "Olson database" time zone names.
+ *
+ * @copyright Copyright (C) 2007-2013 fruux GmbH (https://fruux.com/).
+ * @author Frank Edelhaeuser (fedel@users.sourceforge.net)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://code.google.com/p/sabredav/wiki/License Modified BSD License
+ */
+class TimeZoneUtil {
+
+    public static $map = array(
+
+        // from http://unicode.org/repos/cldr-tmp/trunk/diff/supplemental/zone_tzid.html
+        // snapshot taken on 2012/01/16
+
+        // windows
+        'AUS Central Standard Time'=>'Australia/Darwin',
+        'AUS Eastern Standard Time'=>'Australia/Sydney',
+        'Afghanistan Standard Time'=>'Asia/Kabul',
+        'Alaskan Standard Time'=>'America/Anchorage',
+        'Arab Standard Time'=>'Asia/Riyadh',
+        'Arabian Standard Time'=>'Asia/Dubai',
+        'Arabic Standard Time'=>'Asia/Baghdad',
+        'Argentina Standard Time'=>'America/Buenos_Aires',
+        'Armenian Standard Time'=>'Asia/Yerevan',
+        'Atlantic Standard Time'=>'America/Halifax',
+        'Azerbaijan Standard Time'=>'Asia/Baku',
+        'Azores Standard Time'=>'Atlantic/Azores',
+        'Bangladesh Standard Time'=>'Asia/Dhaka',
+        'Canada Central Standard Time'=>'America/Regina',
+        'Cape Verde Standard Time'=>'Atlantic/Cape_Verde',
+        'Caucasus Standard Time'=>'Asia/Yerevan',
+        'Cen. Australia Standard Time'=>'Australia/Adelaide',
+        'Central America Standard Time'=>'America/Guatemala',
+        'Central Asia Standard Time'=>'Asia/Almaty',
+        'Central Brazilian Standard Time'=>'America/Cuiaba',
+        'Central Europe Standard Time'=>'Europe/Budapest',
+        'Central European Standard Time'=>'Europe/Warsaw',
+        'Central Pacific Standard Time'=>'Pacific/Guadalcanal',
+        'Central Standard Time'=>'America/Chicago',
+        'Central Standard Time (Mexico)'=>'America/Mexico_City',
+        'China Standard Time'=>'Asia/Shanghai',
+        'Dateline Standard Time'=>'Etc/GMT+12',
+        'E. Africa Standard Time'=>'Africa/Nairobi',
+        'E. Australia Standard Time'=>'Australia/Brisbane',
+        'E. Europe Standard Time'=>'Europe/Minsk',
+        'E. South America Standard Time'=>'America/Sao_Paulo',
+        'Eastern Standard Time'=>'America/New_York',
+        'Egypt Standard Time'=>'Africa/Cairo',
+        'Ekaterinburg Standard Time'=>'Asia/Yekaterinburg',
+        'FLE Standard Time'=>'Europe/Kiev',
+        'Fiji Standard Time'=>'Pacific/Fiji',
+        'GMT Standard Time'=>'Europe/London',
+        'GTB Standard Time'=>'Europe/Istanbul',
+        'Georgian Standard Time'=>'Asia/Tbilisi',
+        'Greenland Standard Time'=>'America/Godthab',
+        'Greenwich Standard Time'=>'Atlantic/Reykjavik',
+        'Hawaiian Standard Time'=>'Pacific/Honolulu',
+        'India Standard Time'=>'Asia/Calcutta',
+        'Iran Standard Time'=>'Asia/Tehran',
+        'Israel Standard Time'=>'Asia/Jerusalem',
+        'Jordan Standard Time'=>'Asia/Amman',
+        'Kamchatka Standard Time'=>'Asia/Kamchatka',
+        'Korea Standard Time'=>'Asia/Seoul',
+        'Magadan Standard Time'=>'Asia/Magadan',
+        'Mauritius Standard Time'=>'Indian/Mauritius',
+        'Mexico Standard Time'=>'America/Mexico_City',
+        'Mexico Standard Time 2'=>'America/Chihuahua',
+        'Mid-Atlantic Standard Time'=>'Etc/GMT-2',
+        'Middle East Standard Time'=>'Asia/Beirut',
+        'Montevideo Standard Time'=>'America/Montevideo',
+        'Morocco Standard Time'=>'Africa/Casablanca',
+        'Mountain Standard Time'=>'America/Denver',
+        'Mountain Standard Time (Mexico)'=>'America/Chihuahua',
+        'Myanmar Standard Time'=>'Asia/Rangoon',
+        'N. Central Asia Standard Time'=>'Asia/Novosibirsk',
+        'Namibia Standard Time'=>'Africa/Windhoek',
+        'Nepal Standard Time'=>'Asia/Katmandu',
+        'New Zealand Standard Time'=>'Pacific/Auckland',
+        'Newfoundland Standard Time'=>'America/St_Johns',
+        'North Asia East Standard Time'=>'Asia/Irkutsk',
+        'North Asia Standard Time'=>'Asia/Krasnoyarsk',
+        'Pacific SA Standard Time'=>'America/Santiago',
+        'Pacific Standard Time'=>'America/Los_Angeles',
+        'Pacific Standard Time (Mexico)'=>'America/Santa_Isabel',
+        'Pakistan Standard Time'=>'Asia/Karachi',
+        'Paraguay Standard Time'=>'America/Asuncion',
+        'Romance Standard Time'=>'Europe/Paris',
+        'Russian Standard Time'=>'Europe/Moscow',
+        'SA Eastern Standard Time'=>'America/Cayenne',
+        'SA Pacific Standard Time'=>'America/Bogota',
+        'SA Western Standard Time'=>'America/La_Paz',
+        'SE Asia Standard Time'=>'Asia/Bangkok',
+        'Samoa Standard Time'=>'Pacific/Apia',
+        'Singapore Standard Time'=>'Asia/Singapore',
+        'South Africa Standard Time'=>'Africa/Johannesburg',
+        'Sri Lanka Standard Time'=>'Asia/Colombo',
+        'Syria Standard Time'=>'Asia/Damascus',
+        'Taipei Standard Time'=>'Asia/Taipei',
+        'Tasmania Standard Time'=>'Australia/Hobart',
+        'Tokyo Standard Time'=>'Asia/Tokyo',
+        'Tonga Standard Time'=>'Pacific/Tongatapu',
+        'US Eastern Standard Time'=>'America/Indianapolis',
+        'US Mountain Standard Time'=>'America/Phoenix',
+        'UTC+12'=>'Etc/GMT-12',
+        'UTC-02'=>'Etc/GMT+2',
+        'UTC-11'=>'Etc/GMT+11',
+        'Ulaanbaatar Standard Time'=>'Asia/Ulaanbaatar',
+        'Venezuela Standard Time'=>'America/Caracas',
+        'Vladivostok Standard Time'=>'Asia/Vladivostok',
+        'W. Australia Standard Time'=>'Australia/Perth',
+        'W. Central Africa Standard Time'=>'Africa/Lagos',
+        'W. Europe Standard Time'=>'Europe/Berlin',
+        'West Asia Standard Time'=>'Asia/Tashkent',
+        'West Pacific Standard Time'=>'Pacific/Port_Moresby',
+        'Yakutsk Standard Time'=>'Asia/Yakutsk',
+
+        // Microsoft exchange timezones
+        // Source:
+        // http://msdn.microsoft.com/en-us/library/ms988620%28v=exchg.65%29.aspx
+        //
+        // Correct timezones deduced with help from:
+        // http://en.wikipedia.org/wiki/List_of_tz_database_time_zones
+        'Universal Coordinated Time' => 'UTC',
+        'Casablanca, Monrovia' => 'Africa/Casablanca',
+        'Greenwich Mean Time: Dublin, Edinburgh, Lisbon, London' => 'Europe/Lisbon',
+        'Greenwich Mean Time; Dublin, Edinburgh, London' =>  'Europe/London',
+        'Amsterdam, Berlin, Bern, Rome, Stockholm, Vienna' => 'Europe/Berlin',
+        'Belgrade, Pozsony, Budapest, Ljubljana, Prague' => 'Europe/Prague',
+        'Brussels, Copenhagen, Madrid, Paris' => 'Europe/Paris',
+        'Paris, Madrid, Brussels, Copenhagen' => 'Europe/Paris',
+        'Prague, Central Europe' => 'Europe/Prague',
+        'Sarajevo, Skopje, Sofija, Vilnius, Warsaw, Zagreb' => 'Europe/Sarajevo',
+        'West Central Africa' => 'Africa/Luanda', // This was a best guess
+        'Athens, Istanbul, Minsk' => 'Europe/Athens',
+        'Bucharest' => 'Europe/Bucharest',
+        'Cairo' => 'Africa/Cairo',
+        'Harare, Pretoria' => 'Africa/Harare',
+        'Helsinki, Riga, Tallinn' => 'Europe/Helsinki',
+        'Israel, Jerusalem Standard Time' => 'Asia/Jerusalem',
+        'Baghdad' => 'Asia/Baghdad',
+        'Arab, Kuwait, Riyadh' => 'Asia/Kuwait',
+        'Moscow, St. Petersburg, Volgograd' => 'Europe/Moscow',
+        'East Africa, Nairobi' => 'Africa/Nairobi',
+        'Tehran' => 'Asia/Tehran',
+        'Abu Dhabi, Muscat' => 'Asia/Muscat', // Best guess
+        'Baku, Tbilisi, Yerevan' => 'Asia/Baku',
+        'Kabul' => 'Asia/Kabul',
+        'Ekaterinburg' => 'Asia/Yekaterinburg',
+        'Islamabad, Karachi, Tashkent' => 'Asia/Karachi',
+        'Kolkata, Chennai, Mumbai, New Delhi, India Standard Time' => 'Asia/Calcutta',
+        'Kathmandu, Nepal' => 'Asia/Kathmandu',
+        'Almaty, Novosibirsk, North Central Asia' => 'Asia/Almaty',
+        'Astana, Dhaka' => 'Asia/Dhaka',
+        'Sri Jayawardenepura, Sri Lanka' => 'Asia/Colombo',
+        'Rangoon' => 'Asia/Rangoon',
+        'Bangkok, Hanoi, Jakarta' => 'Asia/Bangkok',
+        'Krasnoyarsk' => 'Asia/Krasnoyarsk',
+        'Beijing, Chongqing, Hong Kong SAR, Urumqi' => 'Asia/Shanghai',
+        'Irkutsk, Ulaan Bataar' => 'Asia/Irkutsk',
+        'Kuala Lumpur, Singapore' => 'Asia/Singapore',
+        'Perth, Western Australia' => 'Australia/Perth',
+        'Taipei' => 'Asia/Taipei',
+        'Osaka, Sapporo, Tokyo' => 'Asia/Tokyo',
+        'Seoul, Korea Standard time' => 'Asia/Seoul',
+        'Yakutsk' => 'Asia/Yakutsk',
+        'Adelaide, Central Australia' => 'Australia/Adelaide',
+        'Darwin' => 'Australia/Darwin',
+        'Brisbane, East Australia' => 'Australia/Brisbane',
+        'Canberra, Melbourne, Sydney, Hobart (year 2000 only)' => 'Australia/Sydney',
+        'Guam, Port Moresby' => 'Pacific/Guam',
+        'Hobart, Tasmania' => 'Australia/Hobart',
+        'Vladivostok' => 'Asia/Vladivostok',
+        'Magadan, Solomon Is., New Caledonia' => 'Asia/Magadan',
+        'Auckland, Wellington' => 'Pacific/Auckland',
+        'Fiji Islands, Kamchatka, Marshall Is.' => 'Pacific/Fiji',
+        'Nuku\'alofa, Tonga' => 'Pacific/Tongatapu',
+        'Azores' => 'Atlantic/Azores',
+        'Cape Verde Is.' => 'Atlantic/Cape_Verde',
+        'Mid-Atlantic' => 'America/Noronha',
+        'Brasilia' => 'America/Sao_Paulo', // Best guess
+        'Buenos Aires' => 'America/Argentina/Buenos_Aires',
+        'Greenland' => 'America/Godthab',
+        'Newfoundland' => 'America/St_Johns',
+        'Atlantic Time (Canada)' => 'America/Halifax',
+        'Caracas, La Paz' => 'America/Caracas',
+        'Santiago' => 'America/Santiago',
+        'Bogota, Lima, Quito' => 'America/Bogota',
+        'Eastern Time (US & Canada)' => 'America/New_York',
+        'Indiana (East)' => 'America/Indiana/Indianapolis',
+        'Central America' => 'America/Guatemala',
+        'Central Time (US & Canada)' => 'America/Chicago',
+        'Mexico City, Tegucigalpa' => 'America/Mexico_City',
+        'Saskatchewan' => 'America/Edmonton',
+        'Arizona' => 'America/Phoenix',
+        'Mountain Time (US & Canada)' => 'America/Denver', // Best guess
+        'Pacific Time (US & Canada); Tijuana' => 'America/Los_Angeles', // Best guess
+        'Alaska' => 'America/Anchorage',
+        'Hawaii' => 'Pacific/Honolulu',
+        'Midway Island, Samoa' => 'Pacific/Midway',
+        'Eniwetok, Kwajalein, Dateline Time' => 'Pacific/Kwajalein',
+
+        // The following list are timezone names that could be generated by
+        // Lotus / Domino
+        'Dateline'               => 'Etc/GMT-12',
+        'Samoa'                  => 'Pacific/Apia',
+        'Hawaiian'               => 'Pacific/Honolulu',
+        'Alaskan'                => 'America/Anchorage',
+        'Pacific'                => 'America/Los_Angeles',
+        'Pacific Standard Time'  => 'America/Los_Angeles',
+        'Mexico Standard Time 2' => 'America/Chihuahua',
+        'Mountain'               => 'America/Denver',
+        'Mountain Standard Time' => 'America/Chihuahua',
+        'US Mountain'            => 'America/Phoenix',
+        'Canada Central'         => 'America/Edmonton',
+        'Central America'        => 'America/Guatemala',
+        'Central'                => 'America/Chicago',
+        'Central Standard Time'  => 'America/Mexico_City',
+        'Mexico'                 => 'America/Mexico_City',
+        'Eastern'                => 'America/New_York',
+        'SA Pacific'             => 'America/Bogota',
+        'US Eastern'             => 'America/Indiana/Indianapolis',
+        'Venezuela'              => 'America/Caracas',
+        'Atlantic'               => 'America/Halifax',
+        'Central Brazilian'      => 'America/Manaus',
+        'Pacific SA'             => 'America/Santiago',
+        'SA Western'             => 'America/La_Paz',
+        'Newfoundland'           => 'America/St_Johns',
+        'Argentina'              => 'America/Argentina/Buenos_Aires',
+        'E. South America'       => 'America/Belem',
+        'Greenland'              => 'America/Godthab',
+        'Montevideo'             => 'America/Montevideo',
+        'SA Eastern'             => 'America/Belem',
+        'Mid-Atlantic'           => 'Etc/GMT-2',
+        'Azores'                 => 'Atlantic/Azores',
+        'Cape Verde'             => 'Atlantic/Cape_Verde',
+        'Greenwich'              => 'Atlantic/Reykjavik', // No I'm serious.. Greenwich is not GMT.
+        'Morocco'                => 'Africa/Casablanca',
+        'Central Europe'         => 'Europe/Prague',
+        'Central European'       => 'Europe/Sarajevo',
+        'Romance'                => 'Europe/Paris',
+        'W. Central Africa'      => 'Africa/Lagos', // Best guess
+        'W. Europe'              => 'Europe/Amsterdam',
+        'E. Europe'              => 'Europe/Minsk',
+        'Egypt'                  => 'Africa/Cairo',
+        'FLE'                    => 'Europe/Helsinki',
+        'GTB'                    => 'Europe/Athens',
+        'Israel'                 => 'Asia/Jerusalem',
+        'Jordan'                 => 'Asia/Amman',
+        'Middle East'            => 'Asia/Beirut',
+        'Namibia'                => 'Africa/Windhoek',
+        'South Africa'           => 'Africa/Harare',
+        'Arab'                   => 'Asia/Kuwait',
+        'Arabic'                 => 'Asia/Baghdad',
+        'E. Africa'              => 'Africa/Nairobi',
+        'Georgian'               => 'Asia/Tbilisi',
+        'Russian'                => 'Europe/Moscow',
+        'Iran'                   => 'Asia/Tehran',
+        'Arabian'                => 'Asia/Muscat',
+        'Armenian'               => 'Asia/Yerevan',
+        'Azerbijan'              => 'Asia/Baku',
+        'Caucasus'               => 'Asia/Yerevan',
+        'Mauritius'              => 'Indian/Mauritius',
+        'Afghanistan'            => 'Asia/Kabul',
+        'Ekaterinburg'           => 'Asia/Yekaterinburg',
+        'Pakistan'               => 'Asia/Karachi',
+        'West Asia'              => 'Asia/Tashkent',
+        'India'                  => 'Asia/Calcutta',
+        'Sri Lanka'              => 'Asia/Colombo',
+        'Nepal'                  => 'Asia/Kathmandu',
+        'Central Asia'           => 'Asia/Dhaka',
+        'N. Central Asia'        => 'Asia/Almaty',
+        'Myanmar'                => 'Asia/Rangoon',
+        'North Asia'             => 'Asia/Krasnoyarsk',
+        'SE Asia'                => 'Asia/Bangkok',
+        'China'                  => 'Asia/Shanghai',
+        'North Asia East'        => 'Asia/Irkutsk',
+        'Singapore'              => 'Asia/Singapore',
+        'Taipei'                 => 'Asia/Taipei',
+        'W. Australia'           => 'Australia/Perth',
+        'Korea'                  => 'Asia/Seoul',
+        'Tokyo'                  => 'Asia/Tokyo',
+        'Yakutsk'                => 'Asia/Yakutsk',
+        'AUS Central'            => 'Australia/Darwin',
+        'Cen. Australia'         => 'Australia/Adelaide',
+        'AUS Eastern'            => 'Australia/Sydney',
+        'E. Australia'           => 'Australia/Brisbane',
+        'Tasmania'               => 'Australia/Hobart',
+        'Vladivostok'            => 'Asia/Vladivostok',
+        'West Pacific'           => 'Pacific/Guam',
+        'Central Pacific'        => 'Asia/Magadan',
+        'Fiji'                   => 'Pacific/Fiji',
+        'New Zealand'            => 'Pacific/Auckland',
+        'Tonga'                  => 'Pacific/Tongatapu',
+    );
+
+    /**
+     * List of microsoft exchange timezone ids.
+     *
+     * Source: http://msdn.microsoft.com/en-us/library/aa563018(loband).aspx
+     */
+    public static $microsoftExchangeMap = array(
+        0  => 'UTC',
+        31 => 'Africa/Casablanca',
+
+        // Insanely, id #2 is used for both Europe/Lisbon, and Europe/Sarajevo.
+        // I'm not even kidding.. We handle this special case in the
+        // getTimeZone method.
+        2  => 'Europe/Lisbon',
+        1  => 'Europe/London',
+        4  => 'Europe/Berlin',
+        6  => 'Europe/Prague',
+        3  => 'Europe/Paris',
+        69 => 'Africa/Luanda', // This was a best guess
+        7  => 'Europe/Athens',
+        5  => 'Europe/Bucharest',
+        49 => 'Africa/Cairo',
+        50 => 'Africa/Harare',
+        59 => 'Europe/Helsinki',
+        27 => 'Asia/Jerusalem',
+        26 => 'Asia/Baghdad',
+        74 => 'Asia/Kuwait',
+        51 => 'Europe/Moscow',
+        56 => 'Africa/Nairobi',
+        25 => 'Asia/Tehran',
+        24 => 'Asia/Muscat', // Best guess
+        54 => 'Asia/Baku',
+        48 => 'Asia/Kabul',
+        58 => 'Asia/Yekaterinburg',
+        47 => 'Asia/Karachi',
+        23 => 'Asia/Calcutta',
+        62 => 'Asia/Kathmandu',
+        46 => 'Asia/Almaty',
+        71 => 'Asia/Dhaka',
+        66 => 'Asia/Colombo',
+        61 => 'Asia/Rangoon',
+        22 => 'Asia/Bangkok',
+        64 => 'Asia/Krasnoyarsk',
+        45 => 'Asia/Shanghai',
+        63 => 'Asia/Irkutsk',
+        21 => 'Asia/Singapore',
+        73 => 'Australia/Perth',
+        75 => 'Asia/Taipei',
+        20 => 'Asia/Tokyo',
+        72 => 'Asia/Seoul',
+        70 => 'Asia/Yakutsk',
+        19 => 'Australia/Adelaide',
+        44 => 'Australia/Darwin',
+        18 => 'Australia/Brisbane',
+        76 => 'Australia/Sydney',
+        43 => 'Pacific/Guam',
+        42 => 'Australia/Hobart',
+        68 => 'Asia/Vladivostok',
+        41 => 'Asia/Magadan',
+        17 => 'Pacific/Auckland',
+        40 => 'Pacific/Fiji',
+        67 => 'Pacific/Tongatapu',
+        29 => 'Atlantic/Azores',
+        53 => 'Atlantic/Cape_Verde',
+        30 => 'America/Noronha',
+         8 => 'America/Sao_Paulo', // Best guess
+        32 => 'America/Argentina/Buenos_Aires',
+        60 => 'America/Godthab',
+        28 => 'America/St_Johns',
+         9 => 'America/Halifax',
+        33 => 'America/Caracas',
+        65 => 'America/Santiago',
+        35 => 'America/Bogota',
+        10 => 'America/New_York',
+        34 => 'America/Indiana/Indianapolis',
+        55 => 'America/Guatemala',
+        11 => 'America/Chicago',
+        37 => 'America/Mexico_City',
+        36 => 'America/Edmonton',
+        38 => 'America/Phoenix',
+        12 => 'America/Denver', // Best guess
+        13 => 'America/Los_Angeles', // Best guess
+        14 => 'America/Anchorage',
+        15 => 'Pacific/Honolulu',
+        16 => 'Pacific/Midway',
+        39 => 'Pacific/Kwajalein',
+    );
+
+    /**
+     * This method will try to find out the correct timezone for an iCalendar
+     * date-time value.
+     *
+     * You must pass the contents of the TZID parameter, as well as the full
+     * calendar.
+     *
+     * If the lookup fails, this method will return the default PHP timezone
+     * (as configured using date_default_timezone_set, or the date.timezone ini
+     * setting).
+     *
+     * Alternatively, if $failIfUncertain is set to true, it will throw an
+     * exception if we cannot accurately determine the timezone.
+     *
+     * @param string $tzid
+     * @param Sabre\VObject\Component $vcalendar
+     * @return DateTimeZone
+     */
+    static public function getTimeZone($tzid, Component $vcalendar = null, $failIfUncertain = false) {
+
+        // First we will just see if the tzid is a support timezone identifier.
+        try {
+            return new \DateTimeZone($tzid);
+        } catch (\Exception $e) {
+        }
+
+        // Next, we check if the tzid is somewhere in our tzid map.
+        if (isset(self::$map[$tzid])) {
+            return new \DateTimeZone(self::$map[$tzid]);
+        }
+
+        // Maybe the author was hyper-lazy and just included an offset. We
+        // support it, but we aren't happy about it.
+        if (preg_match('/^GMT(\+|-)([0-9]{4})$/', $tzid, $matches)) {
+            return new \DateTimeZone('Etc/GMT' . $matches[1] . ltrim(substr($matches[2],0,2),'0'));
+        }
+
+        if ($vcalendar) {
+
+            // If that didn't work, we will scan VTIMEZONE objects
+            foreach($vcalendar->select('VTIMEZONE') as $vtimezone) {
+
+                if ((string)$vtimezone->TZID === $tzid) {
+
+                    // Some clients add 'X-LIC-LOCATION' with the olson name.
+                    if (isset($vtimezone->{'X-LIC-LOCATION'})) {
+
+                        $lic = (string)$vtimezone->{'X-LIC-LOCATION'};
+
+                        // Libical generators may specify strings like
+                        // "SystemV/EST5EDT". For those we must remove the
+                        // SystemV part.
+                        if (substr($lic,0,8)==='SystemV/') {
+                            $lic = substr($lic,8);
+                        }
+
+                        try {
+                            return new \DateTimeZone($lic);
+                        } catch (\Exception $e) {
+                        }
+
+                    }
+                    // Microsoft may add a magic number, which we also have an
+                    // answer for.
+                    if (isset($vtimezone->{'X-MICROSOFT-CDO-TZID'})) {
+                        $cdoId = (int)$vtimezone->{'X-MICROSOFT-CDO-TZID'}->value;
+
+                        // 2 can mean both Europe/Lisbon and Europe/Sarajevo.
+                        if ($cdoId===2 && strpos((string)$vtimezone->TZID, 'Sarajevo')!==false) {
+                            return new \DateTimeZone('Europe/Sarajevo');
+                        }
+
+                        if (isset(self::$microsoftExchangeMap[$cdoId])) {
+                            return new \DateTimeZone(self::$microsoftExchangeMap[$cdoId]);
+                        }
+                    }
+
+                }
+
+            }
+
+        }
+
+        if ($failIfUncertain) {
+            throw new \InvalidArgumentException('We were unable to determine the correct PHP timezone for tzid: ' . $tzid);
+        }
+
+        // If we got all the way here, we default to UTC.
+        return new \DateTimeZone(date_default_timezone_get());
+
+    }
+
+}