Getting a timezone error in /var/log/messages every few seconds

I’m getting the following error message every few seconds, sometimes several a second, in /var/log/messages. It seems to indicate that I need to edit the date.timezone setting but I can’t find which file I am supposed to edit. Anyone know what file it is expecting me to edit or what I need to do to get rid of the error message?

We’re using NTP for time resolution and time/date are being displayed correctly. The system is running FreePBX Hardware is Digium TE110P, Pentium Dual Core, 1Gb RAM, 3ware SATA raid, Snom phones.

Feb 14 11:40:15 trixbox1 php: /var/lib/asterisk/agi-bin/phpagi-asmanager.php[731]: 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 ‘CST/-6.0/no DST’ instead

I’m experiencing the same problem you’re reporting, and we’re not alone.

There’s a thread on this in a trixbox forum which points us to /etc/php.ini as the file to modify.
I don’t find any option in php.ini that I could “change”; but perhaps it’s actually a matter of adding the value rather than changing it.

I figure I’ll spend some time on a text box checking to see if I stand to do any damage by “adding” the instructed date.timezone value.

If anyone has a solution or more information, I would love to hear it.