After the domain expires, the grace period to renew the domain name is actually 40 days. The domain enters the Redemption Period for 30 days after the grace period ends.
However, expires domains should be renewed as soon as possible if the owner plans to keep it. It is not wise to wait till the very last day of the grace period. Domain renewals does take some time to process, so the domain may enter the Redemption Period first before the domain is renewed.