I tried the latest version and it seems that anybody who opens the database and its calendar is able to see all the entries. While it makes sense to see when colleagues are out of office for vacation, training and so on, I think it not a good idea to have access to everybody's sick days count. There should be the possibility to hide certain leave types from the default user.

Second, as the administrator it should be possible to enter sick days and maybe other leave types skipping the approval procedure. It simply doesn't make sense to have a sick day approved. If I'm sick I'm at home there's no way it can be denied. Of course, it's important to keep track of these days so they have to entered in the database.