What should the RSVP date be?

You need to work back from when you need the information. For example, in our case, we were renting accommodations for all the guests, and the last day to cancel part of them was 30 days before. For others, it may be the date that the caterer needs final numbers.

You then want the RSVP date to be a week or two before that drop dead date. This allows you time to call, e-mail, or send carrier pigeons to anyone who does not RSVP. (And trust me, there will be some like that.)

Ours is 1 week before the final count is due (which is 3 weeks before the wedding). I sent them out the beginning of June so they have about 7 weeks to reply.

I will be doing 3 weeks before the wedding as well

I am doing 3 weeks before the wedding because our caterer needs a final headcount 10 days prior. That gives time for getting in touch with people who do not rsvp. Ask your vendors when they need final numbers by just to make sure.

I did 1 month before just to round it off. My caterer needed a good head count a week beforehand and I just wanted to have the time to allow to go through them and get everything sorted out with making sure we had enough chairs - or not way too many and little things like that.