TimeZone.php

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<?php
 
class PHPExcel_Shared_TimeZone
{
        /*
         * Default Timezone used for date/time conversions
         *
         * @private
         * @var string
         */
        protected static $_timezone     = 'UTC';
 
        public static function _validateTimeZone($timezone) {
                if (in_array($timezone, DateTimeZone::listIdentifiers())) {
                        return TRUE;
                }
                return FALSE;
        }
 
        public static function setTimeZone($timezone) {
                if (self::_validateTimezone($timezone)) {
                        self::$_timezone = $timezone;
                        return TRUE;
                }
                return FALSE;
        }       //      function setTimezone()
 
 
        public static function getTimeZone() {
                return self::$_timezone;
        }       //      function getTimezone()
 
 
        private static function _getTimezoneTransitions($objTimezone, $timestamp) {
                $allTransitions = $objTimezone->getTransitions();
                $transitions = array();
                foreach($allTransitions as $key => $transition) {
                        if ($transition['ts'] > $timestamp) {
                                $transitions[] = ($key > 0) ? $allTransitions[$key - 1] : $transition;
                                break;
                        }
                        if (empty($transitions)) {
                                $transitions[] = end($allTransitions);
                        }
                }
 
                return $transitions;
        }
 
        public static function getTimeZoneAdjustment($timezone, $timestamp) {
                if ($timezone !== NULL) {
                        if (!self::_validateTimezone($timezone)) {
                                throw new PHPExcel_Exception("Invalid timezone " . $timezone);
                        }
                } else {
                        $timezone = self::$_timezone;
                }
 
                if ($timezone == 'UST') {
                        return 0;
                }
 
                $objTimezone = new DateTimeZone($timezone);
                if (version_compare(PHP_VERSION, '5.3.0') >= 0) {
                        $transitions = $objTimezone->getTransitions($timestamp,$timestamp);
                } else {
                        $transitions = self::_getTimezoneTransitions($objTimezone, $timestamp);
                }
 
                return (count($transitions) > 0) ? $transitions[0]['offset'] : 0;
        }
 
}