i did a Chat with an AMEXTravel.com agent who said the answer is #1.
a ticket issued at 10AM Friday must be cancelled by 10AM Saturday.
related, a PTS agent says the answer is a new #4
a ticket issued at 10AM Friday must be voided by 10AM Monday.
i suspect she was just going by-the-book and that in reality the system would permit the void until end of day Monday.