As mia pointed out, it is 30 days from statement closing date, which can be any date of the month of course. Chase bills AF on the 1st day of a month regardless when your card is opened. In other words if you opened the card on the 2nd or 3rd of a month (you need to literally go pass the 24hrs of the 1st day - dont ask me how do I know), your AF would be billed on the 1st of the following month if the first year fee not waived, or in 2nd year the 1st of the following month of the month your card initially opened.

After that 30 days there is no reversal of the AF. However if you do product change you have 41 days after the statement closing date to get AF full reversal. I do not know for sure if longer than 41 days whether the AF would be refunded prorated. In the past it was. But we do not seem to have recent DPs to confirm it is still the same policy.