Also, please disable third-party plugins and customizations (if there are any) and check if this issue persists. If you use a caching plugin, make sure that caching is disabled for logged-in users.
If the issue still exists, please provide us with more details, such as which dates are not blocked and should be blocked, etc. (you can send screenshots).
P.S. Please post in English (e.g. via Google Translate); this way, questions/answers may also be helpful for others.