I have some custom php code on my workstation that relies on an accurate representation of the local time. At some point before the Mavericks upgrade, I had added the timezone to /etc/php.ini. That time zone change did not carry over after the upgrade. I saw that there was a new file, /etc/php.ini.default, plus copies of the php.ini file that was there before. I added the timezone to /etc/php.ini.default, but it would display incorrectly when I ran phpinfo(). I realized I needed to rename php.ini.default to php.ini. Once I did that and restarted Apache, the correct time zone appeared in phpinfo() and the correct local time was used in my local php code.
What a pain. I hope I got everything, but I’m not sure.