PHP timezone offset incorrect

Question

The following PHP Code:

function serverTimeZone_offset($userTimeZone)
{
    $userDateTimeZone = new DateTimeZone($userTimeZone);
    $userDateTime     = new DateTime("now", $userDateTimeZone);

    $serverTimeZone     = date_default_timezone_get();
    $serverDateTimeZone = new DateTimeZone($serverTimeZone);
    $serverDateTime     = new DateTime("now", $serverDateTimeZone);

    return $serverDateTimeZone->getOffset($userDateTime);
}

function getDefineTimeZone($timezone)
{
    $userDateTimeZone = new DateTimeZone($timezone);
                 return new DateTime("now", $userDateTimeZone);
}

function getServerTimeZone()
{
    $serverTimeZone     = date_default_timezone_get();
    $serverDateTimeZone = new DateTimeZone($serverTimeZone);

    return new DateTime("now", $serverDateTimeZone);
}

$userDateTime   = getDefineTimeZone('America/Curacao');
$serverDateTime = getServerTimeZone();
$timeOffset     = serverTimeZone_offset('America/Curacao');

var_dump($userDateTime);
var_dump($serverDateTime);
var_dump($timeOffset); // the seconds is incorrect ?!?!

// adding the timezone difference
$userDateTime->add(new DateInterval('PT'.$timeOffset.'S'));

var_dump($userDateTime);

Will output:

object(DateTime)[2]
  public 'date' => string '2014-10-22 17:36:39' (length=19)
  public 'timezone_type' => int 3
  public 'timezone' => string 'America/Curacao' (length=15)

object(DateTime)[3]
  public 'date' => string '2014-10-22 23:36:39' (length=19)
  public 'timezone_type' => int 3
  public 'timezone' => string 'Europe/Paris' (length=12)

int 7200

object(DateTime)[2]
  public 'date' => string '2014-10-22 19:36:39' (length=19)
  public 'timezone_type' => int 3
  public 'timezone' => string 'America/Curacao' (length=15)

Which is obviously incorrect. The offset is returning back 7200 seconds (only 2 hours) rather than 21600 seconds (6 hours). Why?

Community · Accepted Answer · 2023-11-17 20:13:27Z

1

I think uou are misinterpreting the behaviour of DateTimeZone::getOffset(). As said in DateTimeZone php docs:

This function returns the offset to GMT for the date/time specified in the datetime parameter. The GMT offset is calculated with the timezone information contained in the DateTimeZone object being used.

So if server timezone is Europe/Paris, then getOffset() will return the 7200 seconds, as Europe/Paris is GMT+01:00, and it is summer time right now, so it is GMT+02:00.

Try using this code instead:

function serverTimeZone_offset($userTimeZone)
{
    $userDateTimeZone = new DateTimeZone($userTimeZone);
    $userDateTime     = new DateTime("now", $userDateTimeZone);

    $serverTimeZone     = date_default_timezone_get();
    $serverDateTimeZone = new DateTimeZone($serverTimeZone);
    $serverDateTime     = new DateTime("now", $serverDateTimeZone);

    return $serverDateTimeZone->getOffset($userDateTime) - $userDateTimeZone->getOffset($userDateTime);
}

edited Nov 17, 2023 at 20:13

CommunityBot

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answered Oct 22, 2014 at 22:38

Kleskowy

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1 Comment

tfont Over a year ago

Awesome! I indeed completely misinterpreted the behavior of getOffset. Thank you for the simplified clarification.

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