I have disabled all plugins and I am getting this error message in the logs:

[08-Apr-2013 10:36:58] PHP Warning:  date_default_timezone_get() [<a href='function.date-default-timezone-get'>function.date-default-timezone-get</a>]: 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/Los_Angeles' for 'PDT/-7.0/DST' instead in /var/www/roundcube/program/include/rcube_config.php on line 408

The date column is complete blank when listing emails for all inbox folders on the server. Below is what I have for the timezone settings in the main.inc.php

....

// use this format for date display (date or strftime format)
$rcmail_config['date_format'] = 'Y-m-d';

// give this choice of date formats to the user to select from
$rcmail_config['date_formats'] = array('Y-m-d', 'd-m-Y', 'Y/m/d', 'm/d/Y', 'd/m/Y', 'd.m.Y', 'j.n.Y');

// use this format for time display (date or strftime format)
$rcmail_config['time_format'] = 'H:i';

// give this choice of time formats to the user to select from
$rcmail_config['time_formats'] = array('G:i', 'H:i', 'g:i a', 'h:i A');

// use this format for short date display (derived from date_format and time_format)
$rcmail_config['date_short'] = 'm/d/Y h:i';

// use this format for detailed date/time formatting (derived from date_format and time_format)
$rcmail_config['date_long'] = 'm/d/Y h:i';

....