Mensagem No site e Area Administrativa

[eduardogcunhald]

Boa tarde pessoal.
Sou usuario novato em joomla e fazendo um novo site aparece a seguinte mensagem tanto na pagina inicial do site como na area administrativa:

Warning: strtotime() [function.strtotime]: 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/Sao_Paulo' for '-2.0/DST' instead in C:\xampp\htdocs\editado\libraries\joomla\utilities\date.php on line 56

Warning: date() [function.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/Sao_Paulo' for '-2.0/DST' instead in C:\xampp\htdocs\editado\libraries\joomla\utilities\date.php on line 198

Warning: date() [function.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/Sao_Paulo' for '-2.0/DST' instead in C:\xampp\htdocs\ceditado\libraries\joomla\utilities\date.php on line 198.

Alguem poderia me ajudar e me dizer como faço para resolver esse "problema"
Desde já agradeço.