Timezone php error

[Beecher Rintoul]

I'm getting the following php error:

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/Anchorage' for 'AKST/-9.0/no DST' 
instead in /usr/local/tinderbox/scripts/webui/module/moduleBuildPorts.php on 
line 111

I can turn off the error, but I'd rather just fix this. 

Any suggestions?

Beech