I keep it simple and a bit cagy. To me the definition of "new" means freshly acquired, like that day. So whenever I buy something that the spousal unit may be overly curious about and I've had it a week I just say that I've had it a while. A handy term of indeterminate time.
If worse comes to worse, new shoes and a purse are the usual cure.
If worse comes to worse, new shoes and a purse are the usual cure.