if she flakes when you confirm the date then she wasn't that interested anyway and you gave her an easy out.. if you don't is that going to make her show up if she's on the fence?
I equate a lot of dating to the way sales works. I did Cutco knives sales for a couple of summers, and had to spend lots of time figuring out ways to make a customer like you and your product enough to buy it. By the time I finally stopped selling them, I had sold well over $12,000 worth of knives in the 3 months I worked there - pretty good considering I was kinda lazy and only did 4 presentations a week.
The difference between me and some of the other sales people who were less successful? 2 things: one, I always asked for the order; and two, once they said "yes" I shut up until they actually wrote the check and gave me the money.
Now, some of the other people in the field were better sales people than me - they could talk a lot better, be more friendly, etc. Heck, they might even ask for the sale and have the customer say "yes, I'll buy." But, at the last minute, you know what they'd do? They'd ask the customer one last time: "So, are you suuuuure you want to get the knives today?" And the customer would stop, think about it for a second, say "hmm, now that I think about it, I don't think I should get them today," and leave the seller without a sale.
This is essentially what you're doing when you call/text a girl to re-confirm a date. If she already said "yes," you've made the sale; however, when you call her the day of to make sure she's going to show you, you're basically giving off the vibe of "are you suuuuuuure you want to go out with me?" A girl can subconsciously read the vibes of doubt you're giving off, and think to herself: "Hmmm, SHOULD I go out with this guy? Now that I think about it, I might not end up liking him... I don't think I should go out with him today."
You have to be confident at every step of the dating process. Re-confirming does not make you look confident. Now, if she's the one that ends up contacting YOU to re-confirm, that's fine - girls are allowed to show a little self-doubt, plus if she's reaching out to YOU she can't be rejecting you, which means there's a better chance of her showing up. As for YOU, the man, you don't need to do this. If anything, you need to get her into the habit of realizing that you're a man that does what he says. Trust me, after a couple of dates where you set it up days in advance and you show up at the designated place at the agreed upon time, she'll stop worrying about you not reconfirming because she'll know you'll show up.