If your php script is not showing correct date and time then it means your script is using date and time zone configured on your server.
If you want to set your own date and time zone for your domain then it can be done in a very simple manner.
[root@Server ~]#nano php.ini
and enter following line.
save and exit from file.
Now create phpininfo page and open it in browser and you will see that date and time zone have been enabled.