Actually, it would be difficult to prove it was willful. A few weeks or a couple of months going from memory?
February is more than a few weeks from May.
From February 28th to May 1st is actually two months or about eight weeks. Trying to convict/indict someone for perjury on this kind of testimony is darned near impossible unless you have a true smoking gun setting out a cover-up. I just picked these dates to show the grey areas.
I think the folks who are angling for a perjury charge are going to be disappointed. It will never happened, IMO. Maybe Holder resigns but even that is a long shot with the election just a year away. It would be an admission of trouble at the top of the Obama administration. Of course, I could be wrong. I was once before.