Reapplying for US Visa before expiry?

[torontonian]

Hi!

I am on study permit in canad and Could you please tell me how much time before shud we reapply for the US tourist visa before it's expiry? I mean I have three months left when my US tourist visa expires, can i get a date for the interview two or one month before the expiry?

Thanks,

[immihelp]

Your question is not clear.