Adjusting time zone in PHP with DateTime / DateTimeZone

Question

There\'s a lot of info on doing time zone adjustments in PHP, but I haven\'t found an answer for specifically what I want to do due to all the noise.

Given a time in

Answer 1

Here are a couple of functions using the DateTime classes. The first one will return the difference in seconds between two timezones. The second returns a "translation" of the time from one timezone to another.

function timezone_diff($tz_from, $tz_to, $time_str = 'now')
{
    $dt = new DateTime($time_str, new DateTimeZone($tz_from));
    $offset_from = $dt->getOffset();
    $timestamp = $dt->getTimestamp();
    $offset_to = $dt->setTimezone(new DateTimezone($tz_to))->setTimestamp($timestamp)->getOffset();
    return $offset_to - $offset_from;
}

function time_translate($tz_from, $tz_to, $time_str = 'now', $format = 'Y-m-d H:i:s')
{
    $dt = new DateTime($time_str, new DateTimezone($tz_from));
    $timestamp = $dt->getTimestamp();
    return $dt->setTimezone(new DateTimezone($tz_to))->setTimestamp($timestamp)->format($format);
}

Demo:

$los_angeles_time = '2009-09-18 05:00:00';
$los_angeles_tz   = 'America/Los_Angeles';
$hawaii_tz        = 'Pacific/Honolulu';

$los_angeles_hawaii_diff = timezone_diff($los_angeles_tz, $hawaii_tz, $los_angeles_time);
echo $los_angeles_hawaii_diff . '
';

$hawaii_time = time_translate($los_angeles_tz, $hawaii_tz, $los_angeles_time);
echo $hawaii_time . '
';