"date(): It is not safe to rely on the system's timezone settings..."

I got this error when I requested to update the [PHP][1] version from 5.2.17 to PHP 5.3.21 on the server. <div style="border:1px solid #990000;padding-left:20px;margin:0 0 10px 0;"> <h4>A PHP Error was encountered</h4> <p>Severity: Warning</p> <p>Message: 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</p> <p>Filename: libraries/Log.php</p> <p>Line Number: 86</p> </div> 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 /filelocation right here/system/libraries/Log.php on line 86 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 /filelocation right here/system/libraries/Log.php on line 99 <div style="border:1px solid #990000;padding-left:20px;margin:0 0 10px 0;"> <h4>A PHP Error was encountered</h4> <p>Severity: Warning</p> <p>Message: 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</p> <p>Filename: libraries/Log.php</p> <p>Line Number: 99</p> </div> [1]: http://en.wikipedia.org/wiki/PHP