Void Future Date Open AP Invoice
Have you tried voiding just like it is? (That would reverse what you had entered.)
If you get a message that you can't void to that date, change the Void Date - leaving the Posting Date as-is if that is how you posted it - and then try to void. (It isn't obvious but you can click into the Void Date field and make changes.)
If the underlying issue is that you can't void with any date, you'll need someone with SQL experience to modify the date in the table.
[Nothing will voiding it will make it appear as if it "never was created". Voiding will provide an audit trail of the transaction being entered and then reversed with the void.
[Since you mentioned you are new to GP, if the problem was with the Due Date being wrong because of the Document Date, you can edit the Due Date of an open, posted transaction at Transactions > Purchasing > Edit Transaction Information.]