So I just got back from not delivering a cake.... to make a long story short, communication on the delivery date was mixed up, and the cake isn't needed till this Saturday (3 days away). The lady is freaking out because now she thinks she is going to get a stale cake.
My question is do I need to redo the cake or will it be ok till then?

The cake will be fine.

Who messed up the date? You or her? If it was her and she wants a new cake then tell her she needs to pay for a whole new cake.

I have no bloody clue where it got messed up. All I have written down is 21st @ 12:30. I thought that it was an odd time for a party, I should have called her to double check.

Totally depends on who messed up the date....

Also depends on what its filled with as to how the cake will be in three days. But no matter what, the customer will already think she's getting stale cake, and may even have it in her head that no matter what, the cake IS stale.

If its her fault, I would just tell her the cake will be fine, and most bakers make cakes a couple days early anyway. And deliver as promised, same cake....because its not your problem.

If it was your mistake...I would explain that the cake will be fine (as long as its not filled with something that will soak into the cake eventually and give a different consistency...) and then I would also offer a discount or a coupon off their next cake, including a free delivery. Also make sure if you refrigerate that they serve only at room temp, at least after two hours of sitting out, or the cake WILL seem stale if served cold.

I say the cake will be fine as well depending on the filling. Once a cake is seeled with icing it will stay good for about 2 weeks. Try it I did. Not that I make my cakes that far ahead of time.
When I take orders I always write the date and he Day just to be sure.

It's a white cake with raspberry cream cheese filling, plus there is a small "smash" cake that is banana filled with fresh bananas covered with home made whipped cream.

I'm just so stinking irritated at myself right now I could scream!

I figured that I would have to redo the smash cake. But that is ok because I'm sure the it wont go to waste.

And the cake in a box in the fridge. I just keep seeing things that yes yes it will last in the fridge for 10 days, and others that say after 24 hours in the fridge the cake will dry out. I have never had this problem before so I'm a little lost. It's a learning experience that's for sure!

I'd redo it.

She's gonna ask you if you did. If you tell her no, then she will not be happy.

Is it overly decorated? If so, can you salvage some of the decorations?

On a super busy weekend, I've done cakes as early as 3 days in advance before.

Not regularly, but I've done it.

The catering place I worked routinely started cakes (crumb coat, fill) on Tuesday and some of them didn't get served until Sunday.

I would just tell the customer that many bakeries do cakes that early anyway, it just so happens that she accidentally delivered it too early. And I'd give a future (or current) discount and a coupon for free delivery for the next cake.

One thing that I do is, about three weeks before the cake is due (and when their final balance payment is due) I send a confirmation email or phone call (email preferred) listing the delivery or pickup time/location and asking them to confirm it back, along with asking for payment.

Then, a couple of days before the cake is to be delivered I send another email stating that I am just confirming with them and that I will be there on so and so date at such a time.

This is my method and it works for me. Helps to head off mistakes.

If you don't redo that cake, you're going to hear about it. I'm just saying.
She's going to scream to anyone who'll listen if you don't, no matter how fine the cake will be. Doesn't matter whose fault it is. Doesn't matter if that baby would last until next year's bday without spoilage. Doesn't matter.
I would contact her and tell her that you will be rebaking the cake, otherwise it doesn't matter how "fine" the cake will be, to her it isn't "fresh."
SH$@ happens, just gotta deal with it as best you can!

I had a customer that I mixed up and delivered a week early. She volunteered to put it into her fridge or freezer for the week. I said, "Oh no, your birthday boy deserves a fresh cake." She couldn't have been happier and I didn't lose a good customer.

I'd probably do another cake - just a hobby baker and I've not done grand or elaborate cakes but I've had the reverse experience. Earlier in the year my mums friend asked me to do a birthday cake for her son, it was his 40th and a party was organised. Well along comes
mother nature with the snow that crippled Britain so the party got cancelled. She phoned me the day she collected it from mums to say she was delighted with the cake but the party was cancelled and asked how long the cake would stay good - fondant covered sponge with buttercream, I said 5 days max. 3 weeks later mum phoned to say Cathy came in today to say how delicious your cake was, they resceduled the party for yesterday and used the same cake and everybody said how good it was. How bad must her cooking be if 3 week old cake is delicious - yuk!