tomorrow. The transfer must be 100% complete. This means the tickets not only need to be transferred by the owner, they need to be accepted by the guest before midnight tonight.

So if you're planning to transfer (or receive a transfer), ensure it gets done soon.

BYU sent out an email saying this:

"Ticket Transfer Deadline: Friday, Dec. 13 at 11:59 p.m.

You may want to transfer your tickets to other members of your party. This allows you and your guests the flexibility to arrive at different times. Your guests must accept the transfer before tonight at midnight. To transfer your tickets, simply sign in to your BYU Tickets account and select transfer tickets. Then, enter the email or mobile phone number of who you would like to send the ticket(s) to. They will sign in to their BYU Tickets account in order to accept the transfer. If they do not have an account, they will be prompted to create one."