How can I easily convert dates from UTC via PHP?

Question

I am storing dates in a MySQL database in datetime fields in UTC. I'm using PHP, and I've called date_timezone_set('UTC') so that all calls to date() (without timestamp) return the date in UTC.

I then have it so a given web site can select its timezone. Now I want dates to display in the site's timezone. So, if I have a date stored as '2009-04-01 15:36:13', it should display for a user in the PDT timezone (-7 hours) as '2009-04-01 08:36:13'.

What is the easiest (least code) method for doing this via PHP? So far all I've thought of is

date('Y-m-d H:i:s', strtotime($Site->getUTCOffset() . ' hours', strtotime(date($utcDate))));

Is there a shorter way?

Answer 1

<?php

  function getNoteDateTimeZone($date = null, $from_dtz = 'US/Central', $to_dtz = null) {
        //$from_zt = 'US/Central'; // Time Zone = -06:00
        if (is_null($date) == FALSE && is_null($from_dtz) == FALSE && is_null($to_dtz) == FALSE) {
            // set TimeZone from
            $time_object = new DateTime($date, new DateTimeZone($from_dtz));
            $time_now_object = new DateTime("now", new DateTimeZone($from_dtz));
            // Change TimeZone
            $time_object->setTimezone(new DateTimeZone(trim($to_dtz)));
            $time_now_object->setTimezone(new DateTimeZone(trim($to_dtz)));
            // Is day = day in $time_now_object, $time_object..?
            if ($time_now_object->format('d') == $time_object->format('d')) {
                return $time_object->format('H:i:s');
            } else {
                return $time_object->format('Y-m-d H:i:s');
            }
        } else {
            return '';
        }
    }
?>

Use sample:

<?php 
 $date = '2008-06-02 20:32:46';
 $dtz = 'America/Argentina/Buenos_Aires';
 echo getNoteDateTimeZone($date, 'US/Central', $dtz); // Out = 2008-06-02 23:32:46
?>

Answer 2

Convert user timezone to server timezone and vice versa, with a single function:

function convertTimeZone($date, $convertTo = 'userTimeZone', $userTimeZone = 'America/Los_Angeles', $serverTimeZone = 'UTC', $format = 'n/j/Y g:i A')
{
    if($convertTo == 'userTimeZone'){
       $dateTime = new DateTime ($date, new DateTimeZone($serverTimeZone));
       $dateTime->setTimezone(new DateTimeZone($userTimeZone));
       return $dateTime->format($format);   
    } else if($convertTo == 'serverTimeZone'){
       $dateTime = new DateTime ($date, new DateTimeZone($userTimeZone));
       $dateTime->setTimezone(new DateTimeZone($serverTimeZone));
       return $dateTime->format($format);   
    }
}

echo convertTimeZone(date('Ydm h:i:s'),'serverTimeZone');