I am trying to do a command line upgrade and I get this fatal error too.
I checked my php.ini and the date.timezone setting is ok and not commented (i.e. date.timezone = "Europe/Paris"). And I verified that this php.ini was correctly loaded with phpinfo.
I tried to modify the .htaccess with php_value date.timezone 'Europe/Paris' and no luck.
I don't undestand since I have done several install with no troubles but this is the first time I tried to do a command line upgrade (which seems to be a great way to do upgrades!).
I modified the upgrade xml file and renamed it to config.xml. I did 2 modifications, the path to the core and the language (fr instead of en).
And then in the terminal I went to the setup directory and run :
php ./index.php --installmode=upgrade
I am running Mamp 1.9 with PHP 5.3.2