As you know, the server hosted for your web site’s time zone might not the time zone that you want as you might purchased a hosting server hosted somewhere from your location.
Hence it is important if you could define the timezone from the server setting instead of working on each of the script.
Although you set set a global value the inc file from each of your script, but isn’t it easier if you set it to your .htaccess file?
Open up your .htaccess file, enter the command as below.
SetEnv TZ location
The location indicate the timezone that you want to set, for more information on the location information, you may refer to the URL as below.