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
