How to fix: mktime(): It is not safe to rely on the system’s timezone settings

You might encounter a similar error message perhaps running wordpress or some other webapp.

[Tue Mar 12 09:41:14 2013] [error] [client] PHP Warning:  mktime(): 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 'Australia/ACT' for 'EST/10.0/no DST' instead in 
/var/www/html/smarty/plugins/function.html_select_date.php on line 192

To resolve either fix the code or an easy fix is edit: /etc/php5/php.ini or /etc/php.ini depending on your operating system.
Look for the line:

;date.timezone = 

and make it:

date.timezone = 'Australia/Brisbane'

See a list of supported timezones from here: