You have to define the default timezone in your php.ini file, or if you are happy with the default that is being selected, you can turn off strict standards messages in your php.ini file. This can probably be done in your admin control panel from your hosting company. You may need to contact them on how to set it since I'm not sure what hosting company and plan you are using. This isn't an issue with your php code, it is an issue with the hosting server itself.