How can I "outsmart" caching? A view returns an event, which occurs on the current day, in a block.
If there is no current event in the database (empty result), a second view is started, which then outputs events from the past.

It is working, when I am logged in. As long as I am logged in, I see correct results, even in the view preview.

If I look at the next day as anonymous user, I don't see the current event; the block displays the view result of the previous day.
Only with a registration attempt the output is updated, no matter whether I logged in, or a registration attempt is started.

In the views I have changed under -> ADVANCED -> cache: „tag based" to "time-based" with duration of 1 hour for query results and output format.

Unfortunately, the result is the same: the output block is not updated according to the new day.
Now I have deactivated the data caching of the view module, in the hope that tomorrow the display is now updated independently.

If this does not work, only to log in once the day to force an update?

Admin/performance:



Modules:



views/settings/advanced:



The View:



The View (extended)
The issue you have is with the module Internal Page Cache for anonymous users. You have several options:

If you want to serve for anonymous users a newly built page on each request the same way as for logged in users, then uninstall the Internal Page Cache module. The dynamic page cache will still cache pages, but does respect the cache contexts and max-age you set on the page elements. 

Performance wise it is not a good idea to do this, so it might be better to configure a max-age for the Internal Page Cache, see this answer https://drupal.stackexchange.com/a/196557/47547, where you use an event subscriber to set an Expires time in the response.

If this is only for Views, another option is to modify the route definition of the view by setting a no_cache option, see this answer https://drupal.stackexchange.com/a/230242/47547

In all cases you need to configure /admin/config/development/performance for external caches like the browser cache.