How to fix this in my website?

01/22/2012 22:27 campomanes25#1
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/Los_Angeles' for '-8.0/no DST' instead in C:\Program Files (x86)\Apache Software Foundation\Apache2.2\htdocs\htdocs\inc\info.panel. php on line 16

How to fix that error?
01/22/2012 23:31 Flyff_Service#2
PHP Code:
// Disables the output of php errors
error_reporting(0);
// Default timezone
date_default_timezone_set("America/Los_Angeles");