I have updated to 1.6.7 and my log files are now being generated in UTC rather than my preferred PST/PDT. I do not use syslog for rcube.
I have adjusted my config.inc.php: $config['log_date_format'] = 'Y-m-d H:i:s'; which is how my previous version of rcube was set. but the logs are now 7 hours advanced (UTC).
Check your PHP settings.
/etc/php.ini date.timezone = America/Los_Angeles
There is also a timezone setting in roundcube, but i think this is what gets displayed to the end user and doesn't affect the time zone used on the server.
./config/defaults.inc.php // use this timezone to display date/time // valid timezone identifiers are listed here: php.net/manual/en/timezones.php // 'auto' will use the browser's timezone settings $config['timezone'] = 'auto';