Exceptions for xmlrpc tests and date functions

Running the xmlrpc tests, I get 29 of the mostly-same exceptions:

date() [function.date]: It is not safe to rely on the system's timezone settings. Please use the date.timezone setting, the TZ environment variable 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 Run-time notice xmlrpc.inc 384-390 xmlrpc_date() - 28 exceptions

mktime() [function.mktime]: It is not safe to rely on the system's timezone settings. Please use the date.timezone setting, the TZ environment variable 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 Run-time notice xmlrpc_test.module 33 xmlrpc_test_manyTypesTest() - 1 exception

From the PHP manual (http://us2.php.net/date):

Every call to a date/time function will generate a E_NOTICE if the time zone is not valid, and/or a E_STRICT message if using the system settings or the TZ environment variable. See also date_default_timezone_set()

I know Drupal has it's own way of handling timezones, but is there a way to pass that info to date_default_timezone_set() so we don't get these test exceptions? Should we be using Drupal's existing format_date?

Using PHP 5.2.4-2ubuntu5.3. The following is the 'date' section of my phpinfo():

date/time support 	enabled
"Olson" Timezone Database Version 	2007.6
Timezone Database 	internal
Default timezone 	America/Chicago