If you have to uninstall AllEvents for some reasons (for example, you want starts from scratch - or maybe after installing and using it, you realize that it doesn't meet your requirement), you can follow the instructions below to get the extension completely uninstalled:
Extensions => Manage => Managemenu item.
When you uninstall AllEvents, the database tables related to the extension won't be uninstalled. By doing that, when you re-install the extension in the future, all the old data will be kept and still be available. If you want to completely removing it, please access to your site database via phpmyadmin, look at all the tables with prefix
allevents and drop these tables