Im on 1.5.2 on Ubuntu 20.04.4 When I add a time_format or date_format option I just get the "Ooops..." message. Even if it's the same as the default: $config['time_format'] = 'H:i'; if I comment out that line it works fine.
Thanks!
FutureX
When you get the Ooops message what does it say in the Roundcube error log? If what you pasted in your post is accurate then its a typo.
$config['time_format'] = 'H:i'; // contains smart quotes
$config['time_format'] = 'H:i'; // no smart quotes
you cannot use smart quotes to enclose strings in PHP.