There have been several questions here discussing about Horcruxes. I came across this question that discusses about the living being (human or otherwise) that should be killed to create a Horcrux. I also read about the people Lord Voldemort killed to create his Horcruxes. And according to JKR,
The receptacle is prepared by dark magic to become the receptacle of a fragmented piece of soul and that that piece of soul deliberately detached from the Master Soul to act as a future safeguard or anchor to life and to safeguard against death.
But one question still remains. Is there a specific duration (after committing murder) within which the Horcrux can be created. For example, say, good old Voldy murders a Muggle, can he create a Horcrux, say, after a month after committing the murder?