For the last week, I've been watching the dip and trying to figure out the optimal time to buy. I'm talking, of course, about my Old Navy shopping cart . A few months ago, I noticed that items I'd added to my cart on the Old Navy app changed day to day. Typically, prices would increase after a day or two, and go back down the next day. Often, I'd hit "checkout" to avoid more price hikes. It was annoying, and I would often blame myself if I let a deal slip by. So I decided to try an experiment.