PHP Upgrade Generates Time Zone Error

Tuesday Aug 21st 20012 my hosting company upgrades PHP from 5.2 to 5.3.15, following the upgrade the errors shown below started showing up. I tried to do a timezone fix posted on this forum without any success.
Any thoughts or ideas on a fix.

I changed the accual folder name of the site to show as (my-site) for security reasons.

First set -----

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 'PDT/-7.0/DST' instead in /home/my-site/public_html/community/inc/profiles.inc.php on line 127

/home/my-site/public_html/community/inc/profiles.inc.php on line 133

/home/my-site/public_html/community/inc/classes/BxDolForm.php on line 531

/home/my=site/public_html/community/inc/utils.inc.php on line 76

/home/my-site/public_html/community/inc/classes/BxDolTemplate.php on line 308

/home/my-site/public_html/community/modules/boonex/spy/classes/BxSpyModule.php on line 744

Second set----

Warning: Cannot modify header information - headers already sent by (output started at /home/my-site/public_html/community/inc/profiles.inc.php:127) in /home/my-

site/public_html/community/inc/classes/BxDolSession.php on line 64

Warning: Cannot modify header information - headers already sent by (output started at /home/my-site/public_html/community/inc/profiles.inc.php:127) in /home/my-

site/public_html/community/inc/design.inc.php on line 133
object{display:none;}

end errors

set the "date.timezone" variable to "America/Los_Angeles" in php.ini ...

I just added,

date_default_timezone_set('Europe/London');

near the top of inc/header.inc.php

you would use

date_default_timezone_set('America/Los_Angeles');

Thanks gentlemen, I should have known that but that would have been to easy. Changed the ini and that works, to bad the upgrade created other memory alloaction errors so haven't fully tested the fix to see if it holds yet, but initially your suggestion worked fine Misterpopper. I' will let you all know if the fix holds.