problem with the installation used for Opnecart

When I take the first step of installation I get this error message:

Strict Standards: date(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected 'America/Chicago' for 'CDT/-5.0/DST' instead in /homepages/23/d504893716/htdocs/kno/tienda/system/startup.php on line 48

Warning: Cannot modify header information - headers already sent by (output started at /homepages/23/d504893716/htdocs/kno/tienda/system/startup.php:48) in /homepages/23/d504893716/htdocs/kno/tienda/system/engine/controller.php on line 22

what I can do?

Edit php.ini and admin/php.ini and add:
Change "America/Chicago" to whatever your timezone is. The full list of available timezones is at http://php.net/manual/en/timezones.php .