You should apply at least 15 days prior to the anticipated due or covered event date, but no later than 10 days after delivery to ensure timely payment of the benefit from the UFT.
If your baby arrives much later than the due date, you can revise your application in SOLAS. Just log back in within 10 days of giving birth. You have to confirm the birth date regardless.
In general you should apply as soon as possible when you know your plans for using your CAR days and any additional child care leave, however keep in mind that you will not be able to apply earlier than two months in advance of the anticipated event. You should also notify your school or work location so they can begin to plan for your absence.