I said "yes to the dress" one year prior. I was quoted a 7-8 month production time so I wanted to be on the safe side to allow enough time for alterations. If your wedding is in August 2021, then I would suggest starting sooner rather than later
We only had a 54 week engagement. I stared looking just under a year out and bought 11 months before. I bought off the rack so it didn’t matter how early I bought. I was worried about having to order and it coming in on time
We got engaged July’19, set the date of 4/3/21 & bought my dress June’20. The boutique I purchased it from is one of those, once you buy it, you walk out the door with it. Scheduling alterations mid January.
My wedding is in June 2022 and I plan to start looking at least a year prior. With Covid, etc., I was advised by the boutiques I'm going to to start looking sooner than later because of possible delays. Because most gowns take at least 8 months to be made, you want to plan accordingly to be on the safe side and allow for alterations, etc. before your big day. The sooner, the better!
I started looking in July of this year for my January 2022 wedding. I went to a couple of shops and found one I’m planning on ordering. They recommended waiting until March-April to order it since my size tends to fluctuate.