How to retrieve timezone offset from GMT+0 in php?

Question

I am no expert in php. I know timezones are supported in PHP.

For a given timezone TZ supported by PHP, I need to retrieve the offset (i.e., number of hours and minutes to add or substract) to a known UTC (i.e. GMT+0) to get that time in the TZ zone.

How can I achieve this? Ultimately, I need to get those offsets for all supported timezones in PHP. Thanks.

Answer 1

This is a simple example how to get timezone offset in seconds:

$dtz = new DateTimeZone('Europe/Sofia');
$time_in_sofia = new DateTime('now', $dtz);
echo $dtz->getOffset( $time_in_sofia );

to display it in the format GMT+x:

$offset = $dtz->getOffset( $time_in_sofia ) / 3600;
echo "GMT" . ($offset < 0 ? $offset : "+".$offset);

working example

Answer 2

This will be useful for converting offset values into GMT format without any calculation

<?php

  //target time zone
  $target_time_zone = new DateTimeZone('America/Los_Angeles');

  //find kolkata time 
  $date_time = new DateTime('now', $target_time_zone);

  //get the exact GMT format
  echo 'GMT '.$date_time->format('P');

Answer 3

This will get you the standard offset (not the one in or out of DST [depending on the time of year]):

function getStandardOffsetUTC($timezone)
{
    if($timezone == 'UTC') {
        return '';
    } else {
        $timezone = new DateTimeZone($timezone);
        $transitions = $timezone->getTransitions(time() - 86400*365, time());

        foreach ($transitions as $transition)
        {
            if ($transition['isdst'])
            {
                continue;
            }

            return sprintf('UTC %+03d:%02u', $transition['offset'] / 3600, abs($transition['offset']) % 3600 / 60);
        }

        return false;
    }
}

Usage:

echo getStandardOffsetUTC('Europe/Sofia'); // UTC +02:00

You can get a peek at the differences here.

Answer 4

It is possible just by the following single line.

echo (new DateTime('now', new DateTimeZone( 'Asia/Kabul' )))->format('P');

Answer 5

For all supported timezones in PHP:

$timezone_offsets = array();

foreach(timezone_identifiers_list() as $timezone_identifier)
{
    $date_time_zone = new DateTimeZone($timezone_identifier);
    $date_time = new DateTime('now', $date_time_zone);
    $timezone_offsets[$timezone_identifier] = $date_time_zone->getOffset($date_time);
}

print_r($timezone_offsets);