The interview invitation will usually come 2-3 weeks before the interview date. When they contact you, they will usually give you a firm date, although I am pretty sure that yo ucan simply call and reschedule if that date doesn't work for you. The HBS admissions office is kind of mysterious, but I remember being impressed by the fact that they seemed to run a really tight ship.
The deadline question is a little bit of a mystery. The invites come in waves, but can keep coming for weeks after the main wave has come. There's no hard date, as far as I know.
As for the location, it will most likely be at HBS. I strongly encourage you to make the trip. Doing so signals your sincere interest in the program. It may seem inconvenient, but remember that there are 1000's of other applicants who would be willing to make the trip in a heartbeat!
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