I found a problem in Yourls. It's not necessarily a problem with the code, but a problem none the less.
In functions.php, the timestamp is being written to the yourls_log and yourls_url db's differently, and depending on how the server is set up, it can cause a problem.
function yourls_log_redirect() writes the time with MySQL's NOW() keyword, while function yourls_insert_link_in_db() writes it with PHP's date('Y-m-d H:i:s'). On the webhost that I'm using, MySQL is using the server's time, not UTC, so it's 4 hours different than PHP's time, since PHP is being set with date_default_timezone_set( 'UTC' );
This drove me nuts for quite awhile until I realized what was going on. Once I switched from NOW() to date('Y-m-d H:i:s') the problem went away and all my times are now the same. I believe both functions should use the same system for time so as to avoid this scenario.
BTW, great script! I know I probably shouldn't ask ;) but... any idea when the next version will be released? I read something about version 2.0 awhile back, but haven't heard anything since.