Here's the answer: If only there was an answer we'd tell you. There are many variations on what happens when a domain passes it's renewal/expiration date. Some that expire fall directly into the domain registrar's auction system. Some are swept into SnapNames auction system. Some have shorter time periods that others between when a domain expires and when the registrar takes action.
In the good old days we might tell you that it's X days until the delete cycle begins but that's just not the answer in 2006.
But no more, as Webwork said there is no known answer to it anymore and the renewal time period is also significantly shorter too.
BTW, if you are hoping to reg an expired name you will find it very tough to do even if you knew the schedule assuming the name has some traffic or consists of real words.
Reading their TOS it said they would usually allow 30 days but not guaranteed.
I can sleep a little better now I have it back.
Cheers