尽管gmdate函数可用。如果您使用的是PHP
5.2或更高版本，请考虑使用DateTime对象。

这是切换到GMT的代码

$date = new DateTime();
$date->setTimezone(new DateTimeZone('GMT'));

然后返回默认时区…

$date = new DateTime('2011-01-01', new DateTimeZone('GMT'));
$date->setTimezone(new DateTimeZone(date_default_timezone_get()));

使用DateTime对象可以像创建过程函数一样创建日期时间，只是保留对实例的引用。

例如

// Get a reference to Christmas of 2011, at lunch time.
$date = new DateTime('2011-12-25 13:00:00');

// Print the date for people to see, in whatever format we specify.
echo $date->format('D jS M y');

// Change the timezone to GMT.
$date->setTimezone(new DateTimeZone('GMT'));

// Now print the date/time it would in the GMT timezone
// as opposed to the default timezone it was created with.
echo $date->format('Y-m-d H:i:s');

// Just to show of some more, get the previous Sunday
$date->modify('previous Sunday');

您可以使用很多功能，这些功能比过程功能更具可读性。

从时区转换为GMT的明确示例

$melbourne = new DateTimeZone('Australia/Melbourne');
$gmt = new DateTimeZone('GMT');

$date = new DateTime('2011-12-25 00:00:00', $melbourne);
$date->setTimezone($gmt);
echo $date->format('Y-m-d H:i:s');
// Output: 2011-12-24 13:00:00
// At midnight on Christmas eve in Melbourne it will be 1pm on Christmas Eve GMT.

echo '<br/>';

// Convert it back to Australia/Melbourne
$date->setTimezone($melbourne);
echo $date->format('Y-m-d H:i:s');

使用您的亚洲/加尔各答前往美国/纽约

date_default_timezone_set('Asia/Kolkata');
$date = new DateTime('2011-03-28 13:00:00');
$date->setTimezone(new DateTimeZone('America/New_York'));
echo $date->format("Y-m-d H:i:s");
//Outputs: 2011-03-28 03:30:00