For a Frozen Embryo Transfer, the due dates on Day 5, Day 6, and Day 7 are the same because the age of the embryo is calculated from the day of the egg retrieval, not the day of the transfer. The embryos are usually frozen on Day 5 or Day 6, and occasionally on Day 7, and are then thawed for transfer. Therefore, the due date is calculated based on the age of the embryo at the time of retrieval, not the transfer.