If you place an order an the item doesn't arrive in time for Zulily's expected ship date, they will send you an e-mail letting you know that it's late and they will give it a few more days. If they know they won't be able to get the item to ship, they will refund to your original form of payment. I've had this happen a few times and not only have they issued a full refund but they've also given me a $10 store credit on top of my full refund.

When that's happened to me they refund my money. Not a credit. But they usually add a credit to your account for your trouble in addition to refunding your original payment type.