While my study of christianity has been lacking as of late I think what it refers to is after death. Jesus wiped the slate clean for all sins and you are free to go to heaven and forgiven of all. As long as you haven't denied him. If you deny him you commit the unforgivable sin and goto hell. The gist is that you have up until you die to accept him even after denial as long as its before your death you are still free to go either way.
I think there is a little cavet hear in that the mark of the beast is equivalient to permanent denial of god.
™ Version 4.2
