Cal asks Bianca what the baby's due date is. She tells him it's February. He then says something to the extent that there are 28 days in February and to narrow it down. She tells him it's the 20th or 21st, it's not an exact science. He then marks an big X on the calendar on what is supposed to be the 20th and 21st of February. The X's are put on a Friday and Saturday. The calendar clearly shows nine additional days in February. February has only 28 days, as Cal mentions. Even if it's a leap year, the calendar shows too many additional days past the 21st.