Im getting an error message:

Warning: 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 'EDT/-4.0/DST' instead in /home/sierra/public_html/shop/libsecure.php on line 516
Invalid or incorrect license key. Please contact us for additional details: IP Address Invalid

the file referenced is a huge hash that is unreadable by humans.

How can i get this fixed?