Ok, I knew it was around 24 - 48 hours, but it is apperently only 24 hours.
Anyways, I found this article: it says that you can flush DNS with ipconfig blabla, also already knew that.
For system administrators, using a is usually implemented using one or more centralized servers that are authoritative for certain domains.
When a client host requests information from a nameserver, it usually connects to port 53.
On the other hand, since the recursive lookup takes far more time than authoritative responses, recursive servers should be available to a restricted number of clients only, otherwise they are prone to distributed denial of service (DDo S) attacks.