Hi WillSuranol,
It should have been obvious; as FluxCP is designed fairly straightforward. If you took the effort to look, you should have seen the following line;
'DateDefaultTimezone' => null, // The default timezone, consult the PHP manual for valid timezones: http://php.net/timezones (null for defaut system TZ)
In order to set it to PHT, you would put:
'DateDefaultTimezone' => 'Asia/Manila', // The default timezone, consult the PHP manual for valid timezones: http://php.net/timezones (null for defaut system TZ)
For other times, you can see within the comment; the link to guide you to proper values for the Timezone: http://php.net/timezones