Fold3 until 23:39 on Monday 31st May.
and
MyHeritage until midnight Tuesday 1st June.
I don't know which time zone applies to the cut offs. I didn't need to register or sign in to either site, though an Ancestry UK login should work on Fold3. I think people have found worldwide records, not just US ones, on other free weekends and a quick spot check for a UK soldier gave records on both sites.
