I have recently upgraded the php version on my web server from version 5.2.17 to version 5.3.x.  The reason was because I had a Joomla extension that needed php 5.3 or better.  I thought everything was ok, until a few days later I was working on a clients Joomla 1.5 site and the homepage had some BIG, NASTY, PHP ERRORS!  I was in a bit of a panic.  I had just installed a new extension on this site, and I clicked over to the front end and found the errors.  At first glance I thought the newly installed extension was the col-prate.  However, after a few Google searches, I found it was a php error populated by the older version of Joomla 1.5 and the new version of php.  I of course don’t develop anymore with Joomla 1.5, but this was a project from while back, and well, upgrading from Joomla 1.5 to Joomla 2.5 can destroy a website causing you to rebuild it from the ground up.  Any-whoot, the errors I saw on the front end of my Joomla 1.5 site were as follows:

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/Chicago' for 'CDT/-5.0/DST' instead in /home/public_html/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/Chicago' for 'CDT/-5.0/DST' instead in /home/public_html/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/Chicago' for 'CDT/-5.0/DST' instead in /home/public_html/libraries/joomla/utilities/date.php on line 198

I consulted Google and kept finding posts that would point me towards updating the date.timezone in the php.ini.  Well, my Joomla 1.5 php.ini file didn’t have this code.  So I simply added the following code to  the very bottom of php.ini in the root folder, and it fixed the problem:

date.timezone = "America/Chicago"