I signed a sublease contract for the next month but I need to know if it's possible to have a new “Anmeldungbescheinigung” (Registering certificate) before moving to it in order to send document to my wife and reduce the waiting time.
Currently and up until November 1 registration law is state matter. None of the state laws regulate whether you can do so.
From November 1 the new federal registration law will be put in place. Unfortunately it still does not regulate that matter. However, an old draft of this law gives valuable insight in how it is supposed to work. It explicitly stated that registration is possible beginning a week before moving. That clause would explicitly codify what is practiced anyway almost everywhere across Germany. I don't know why it was removed later in the drafting process as it was not public at that stage.
The spirit of the duty to register is to have a list of residents which matches reality as closely as possible. Therefore you are required to register no later than two weeks after moving. On the other hand, registering too early would lead to bad data too as plans can change between the registration date and the supposed movement date. So one would need to register as closely to the actual date. As already said, mostly that is supposed to mean one week before that date at maximum (unfortunately I don't have a public reference for that to link to apart from the draft above which states that).
So no, it is not possible to register a month before moving.
Providing a contract with starting date 01/08 and trying to register it in bürgeramt even 1 day before (for me it was on 31 July) is impossible and the agent will ask you to come after one day. That was a very bad situation to wait earlier in the morning then being forced to come another day. So things should be clear now.