DateTime::diff() isn't affected by timezone but always return same value

Question

I am adding auction-based data to my system. For example:

user's timezone  is : `America/Denver`
auction start time is : Thu, 21 Jun 2012 03:46:22 AM
auction period : 1 day.
auction end time : Fri, 22 Jun 2012 03:46:22 AM

I store all these information as it is in my DB (ie all stored time based on user's timezone ).

Now I want the actual difference between end time and current time (of America/Denver timezone).

I used DateTime() functions

so even I don't convert the timezone; it returns same difference (and that is wrong too).

My PHP code is below; you can also find it at CodePad

$end_time = 'Fri, 22 Jun 2012 03:46:22 AM';
$tz = 'America/Denver';
dateDifference($end_time,$tz);

function dateDifference($end, $tz = NULL)
    {
      $owner_tz = new DateTimeZone($tz);
      //var_dump($owner_tz->getName()); 

      $from  = new DateTime("now", new DateTimeZone('GMT'));     
      $from ->setTimeZone($owner_tz);

      $to = new DateTime($end,new DateTimeZone('GMT'));
      /* @Note:I have commented below setTimeZone() because I have already stored 
       * `end time` as per user's  timezone, So I dont need to convert it again 
       * into user's timezone.you can un-comment below line. 
       * it doesn't affect the results anyways.
       */
     //$to ->setTimeZone($owner_tz);        

    //procedural style using date_diff()
    $interval = date_diff($from, $to);        
    var_dump($interval); 

    // OO style using dateTime::diff()
    $interval = $from->diff($to);       
    var_dump($interval);     
}

Returns:

object(DateInterval)[4]
  public 'y' => int 0
  public 'm' => int 0
  public 'd' => int 0
  public 'h' => int 16
  public 'i' => int 40
  public 's' => int 24
  public 'invert' => int 0
  public 'days' => int 6015

References:

• DateTime()
• DateTime::diff
• DateTime::setTimeZone
• Handling timezone conversion with PHP DateTime

Answer 1

On the following lines you're basically saying that the end date is in GMT while it should be in America/Denver time:

$to = new DateTime($end, new DateTimeZone('GMT'));

Then you intent to convert it to America/Denver time but since you created the date using the GMT timezone this would have been wrong anyway.

// $to ->setTimeZone($owner_tz);

This will create the end date using the users timezone which is probably what you are looking for:

$to = new DateTime($end, $owner_tz);

Answer 2

I got the solution, so i would like to share

Actually I have set default timezone in config.inc.php file as below

date_default_timezone_set('America/Los_Angeles');

then I check the current time and timezone of MySQL server from phpmyadmin with below query

SELECT NOW(), SYSDATE(), @@global.time_zone , @@session.time_zone , 
      TIMEDIFF( NOW( ) , CONVERT_TZ( NOW( ) , @@session.time_zone ,  '+00:00' )) 
      AS OFFSET

This return the OFFSET value +05:30

solution steps:

• First I changed the timezone of mySQL Server to GMT/UTC +00:00 ( I have super privilage on mySQL server)

   SET GLOBAL time_zone = '+00:00'; 

• We save the date and time using start_date = NOW() ( column datatype: DATETIME )

Now there is 2 way to get date and time as per user's timezone ( America/Denver )

first method ( using PHP DateTime )

 /*
   * first set timezone as GMT.
   * This is MUST because default timezone is differ from user timezone  
  */     
    $gmt = new DateTimeZone('GMT');
    $user_tz = 'America/Denver';
    $st = new DateTime($row[`start_date`], $gmt);
    // now set user timezone
    $st->setTimezone($user_tz );
    $stime = $qt->format('r');
    echo $stime;

second method (using MySQL UNIX_TIMESTAMP )

#$retrieve data from server in timestamp
$qry = "SELECT `start_date`,UNIX_TIMESTAMP(`start_date`) AS sTimestamp FROM..."  
$st = new DateTime('@'.$row['sTimestamp ']);                     
$stime = $st->format('r');
echo $stime;

Note : dont change start_date to timestamp with strtotime() . It will return different value from the UNIX_TIMESTAMP() ie

 strtotime($row['start_date']) !== $row['sTimestamp']