I would have to think that the date being off by exactly one month, is nothing more than a typo on the part of whoever did the actual typing up of the warrant and not the date requested or agreed to by the signing judge or magistrate. Hence, a typo is not going to invalidate the warrant.
I copied the following from the California penal code:
1534. (a) A search warrant shall be executed and returned within 10
days after date of issuance. A warrant executed within the 10-day
period shall be deemed to have been timely executed and no further
showing of timeliness need be made. After the expiration of 10 days,
the warrant, unless executed, is void. The documents and records of
the court relating to the warrant need not be open to the public
until the execution and return of the warrant or the expiration of
the 10-day period after issuance. Thereafter, if the warrant has
been executed, the documents and records shall be open to the public
as a judicial record.
(b) If a duplicate original search warrant has been executed, the
peace officer who executed the warrant shall enter the exact time of
its execution on its face.
(c) A search warrant may be made returnable before the issuing
magistrate or his court.
So,in light of the above, I don't imagine that any police agency would request a warrant thirty days in advance or that a judge would issue such a warrant. This is why I believe it was simply a typo.
The following information also claims that seized evidence will be allowed to stand if the officers acted in good faith:
Searches, seizures, and arrests made pursuant to a defective warrant may be justified if the officer was proceeding in "good faith." The Supreme Court has said that a search made pursuant to a warrant that is later declared invalid (i.e., it fails to meet the requirements for a valid warrant) will still be considered reasonable under the Fourth Amendment so long as the warrant was issued by a magistrate and the defect was not the result of willful police deception (see United States v. Leon, 468 U.S. 897 [1984]). This exception to the warrant requirement was created so as not to punish honest police officers who have done nothing wrong while acting in accordance with an ostensibly valid warrant.