The real answer is this. Their ToS says it's 12 days but in reality it can go up to 17 days. But don't bank on it. If it's still in your account. RENEW IT NOW!.
for 12 days after the expiration you can renew it in the control panel for the regular price (remember to use coupons for better prices) ...
then , until the 18th day , you can renew the domain by going to the renew panel (second link from the top in the "Domains" tab on the left , in the homepage) because it gets deleted from the domain control panel ... even though I have followed many domains up to the 18th (the exact change happens 1 minute after 23:59 (Arizona Time) of the 18th day towards the 19th day) the official statement from GoDaddy account managers is that the domain stays in that state until the 17th ...
in general , if it is a domain you like , don't leave it for the last minute (or the last day) ... preferably try to renew it before expiration so as not to lose your traffic (the domains usually do not resolve after expiration)
after that the domain goes to redemption and needs $80 (plus renew fees) to be retrieved ...
you can find a more detailed description about redemption here