DateTimeZone exception?

Question

Hi, I have a piece of code under SugarPro/custom/clients/base/api/Tasks.php 
 $utcTime = new DateTime("now", new DateTimeZone("UTC")); 
 it work fine, however when I use the same code in another file SugarPro/custom/modules/Quotes/custom_classes/QuoteNotify.php 
 it will throw exception, the exception is caused by "new DateTimeZone("UTC")" The only different I noticed is that below two line is included in QuoteNotify.php 
 namespace Sugarcrm\Sugarcrm\custom\modules\Quotes\custom_classes; use DateTime; I just wonder why the exception error in QuoteNotify.php? Any suggestion would be appreciated.

Manson ho · Accepted Answer

When using namespace, all classes not defined by anyone of the namespaces need to have "\" as prefix, like: 
 $utcTime = new \DateTime("now", new \DateTimeZone("UTC")); 
 or 
 $utcTime = new DateTime("now", new \DateTimeZone("UTC")); 
 
 Regards