// Simply:
$date = date('Y-m-d H:i:s');

// Or:
$date = date('Y/m/d H:i:s');

// This would return the date in the following formats respectively:
$date = '2012-03-06 17:33:07';
// Or
$date = '2012/03/06 17:33:07';

/** 
 * This time is based on the default server time zone.
 * If you want the date in a different time zone,
 * say if you come from Nairobi, Kenya like I do, you can set
 * the time zone to Nairobi as shown below.
 */

date_default_timezone_set('Africa/Nairobi');

// Then call the date functions
$date = date('Y-m-d H:i:s');
// Or
$date = date('Y/m/d H:i:s');

// date_default_timezone_set() function is however
// supported by PHP version 5.1.0 or above.

有关时区参考，请参见支持的时区列表。

Use:

$date = date('m/d/Y h:i:s a', time());

它的工作原理。

 $date = new DateTime('now', new DateTimeZone('Asia/Kolkata'));
 echo $date->format('d-m-Y H:i:s');

更新

 //Also get am/pm in datetime:
 echo $date->format('d-m-Y H:i:s a'); // output 30-12-2013 10:16:15 am

对于日期格式，PHP date() Function很有用。

Linux服务器时间与PHP time()时区差异如下:

<?php
    putenv("TZ=Asia/Kabul");
    $t = time();
    echo date('d/m/Y H:i:sa', $t);
?>

如果你是孟加拉国人，如果你想知道达卡的时间，那么用这个:

$date = new DateTime();
$date->setTimeZone(new DateTimeZone("Asia/Dhaka"));
$get_datetime = $date->format('d.m.Y H:i:s');

日期格式也取决于:

echo date("d/m/Y H:i:sa"); // 13/04/2017 19:38:15pm