If you get this error listed bellow:
date(): It is not safe to rely on the system's timezone settings
mktime(): It is not safe to rely on the system's timezone settings
You can edit your /etc/php.ini file and search:
date.timezone =
You can edit it eg. like this:
date.timezone ="US/Central"
After editing you can restart apache:
service httpd restart
Time Zone list:
https://php.net/manual/en/timezones.php