When is it too late to be asked/ask someone to prom?

Id draw the line at about a month,only because it seems as if your asking because you have noone better to go with,but it doesn't take that much time to get a dress and make a hair appointment unless your one of those psychos who think the prom is the definition of life and have to look at 18 million stores and book appointments in places where you need to call months in advance.Personally,Id need a week or two.