To be complete, I think Hilton Head is 5 days and Aulani would be 7 days.
When you sign your paperwork you should see a notice that says this:
You may cancel this contract without any penalty or obligation within 10 days after the date you sign this contract. If you decide to cancel this contract, you must notify the seller in writing of your intent to cancel. Your notice of cancellation shall be effective upon the date sent and shall be sent to the seller at (address) . Any attempt to obtain a waiver of your cancellation right is void and of no effect. While you may execute all closing documents in advance, the closing, as evidenced by delivery of the deed or other document, before expiration of your 10-day cancellation period, is prohibited.
If you don't see that notice then, if my reading of the law is correct, you have one year after closing to cancel. But, IANAL.