I think that in the message that they announced the extension April 28. That is to say any one whose sub does not expire before April 28. So I would say that they will wait to do this on April 29 or 28. The addition would take less work on their part to update their database.
I just went back to the announcement and it said 17th. My mistake, but hay the 28th sounds good to me, maybe that is why I had it on the brain. Ha! Ha!