Hi Lindsey! Are you going the traditional route with a bridal salon? If so, NOW!!! It took 11 months for my wedding gown to arrive. Some designers can get them to you faster, but if you fall in love with a gown that will take longer, like mine, you'll need to go soon. I only went one day to a private showing at one salon with my bridal entourage. We had the best time!! Good luck!!
I agree with Victorian Bride. I would order now to be on the safe side if you go with a bridal salon unless you go off the beaten path for your dress like I did. I ordered mine off a bridal resale site called Stillwhite where you talk directly to the bride selling and they ship it to you. Some are used but in great condition and others are brand new/tag still attached like mine. I received my dress within a week after purchase and all I have to do is worry about alterations (which won't be much).