Timezone setting 错误

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/New_York’ for ‘-4.0/DST’ instead in D:\Dkits\Apache2.2\htdocs\mysonicfirewebs\sonicfire\includes\foot.php on line 52